20253907 2025-2026-2《网络攻防实践》第5周作业

1. 实践内容

本次实验我主要学习到了网络安全防范技术，包括防火墙配置、入侵检测系统（Snort）的使用以及蜜网网关的防护机制分析。
实验分为以下三个部分：
防火墙配置：在 Linux 平台（Metasploitable）上使用 iptables 配置防火墙规则，实现以下功能：

• 过滤 ICMP 数据包：通过添加 iptables 规则，丢弃所有 ICMP 协议的数据包，使主机不响应任何 ping 请求。这样可以隐藏主机的在线状态，增加攻击者的探测难度。
• 限制服务访问来源：配置 iptables 的 INPUT 链，设置默认策略为 DROP（拒绝所有入站流量），然后添加允许规则，只放行来自特定 IP（Kali，192.168.200.6）的 TCP 连接，例如 Telnet 服务。其他 IP（如 WinXP，192.168.200.108）的访问请求将被拒绝。通过这种方式，理解基于源 IP 的访问控制原理。

Snort 入侵检测：使用 Snort 对给定的 pcap 文件（listen.pcap）进行入侵检测分析。Snort 是一个开源的网络入侵检测/防御系统（IDS/IPS），能够基于规则匹配检测网络流量中的攻击特征。实验中需要：

• 从离线的 pcap 文件读取网络数据源
• 配置 Snort 输出报警日志（明文格式）
• 分析报警日志，识别出网络扫描攻击行为（如 Nmap SYN 扫描），并说明攻击特征

蜜网网关分析：分析虚拟网络攻防环境中蜜网网关的防火墙和 IDS/IPS 配置规则。蜜网网关（Honeywall）部署在攻击网段和靶机网段之间，以透明网桥模式工作。通过查看其 iptables 规则和 Snort 配置，理解蜜网网关如何：

• 利用防火墙规则控制进出蜜网的流量（如限制出站连接、标记可疑流量）
• 利用入侵检测系统实时分析流量并产生告警
• 结合 Sebek 等数据捕获工具记录攻击者的操作，实现攻击数据的完整捕获与控制需求

2. 实践过程

2.1 防火墙配置

2.1.1 过滤 ICMP 数据包

实验目标：在 Metasploitable 上配置防火墙规则，使其不响应 ping 请求。

操作步骤：

1. 查看当前防火墙规则：
   在 Metasploitable 上执行：

   sudo iptables -L
   

   初始状态通常没有规则，所有链的默认策略为 ACCEPT。
   

2. 测试 ping 连通性（攻击前）：
   在 Kali 上 ping Metasploitable：

   ping -c 4 192.168.200.130
   

   

3. 添加 ICMP 过滤规则：
   在 Metasploitable 上执行：

   sudo iptables -A INPUT -p icmp -j DROP
   

   这条规则的含义是：在 INPUT 链末尾追加一条规则，对所有 ICMP 协议的数据包执行 DROP（丢弃）操作。
   再输入

   sudo iptables -L
   

   可以看到 DROP icmp -- anywhere anywhere 的规则。
   

4. 再次测试 ping：
   在 Kali 上再次 ping Metasploitable：

   ping -c 4 192.168.200.130
   

   此时应显示 100% packet loss，无法收到回复。
   

2.1.2 只允许特定 IP 访问服务

实验目标：配置防火墙，只允许 Kali（192.168.200.6）访问 Metasploitable 的 Telnet 服务，WinXP（192.168.200.108）无法访问。

操作步骤：

1. 确认服务正常：
   在 Kali 上测试 Telnet 连接：

   telnet 192.168.200.130
   

   
   在 WinXP 上也进行相同测试，确认都能正常连接。
   

2. 设置默认策略为 DROP：
   在 Metasploitable 上执行：

   sudo iptables -P INPUT DROP
   

   允许特定 IP 访问：

   sudo iptables -A INPUT -p tcp -s 192.168.200.6 -j ACCEPT
   

   这将 INPUT 链的默认策略改为 DROP，即除了明确允许的流量外，其他所有入站流量都被拒绝。
   

3. 测试访问：

   • 在 Kali 上再次 telnet 192.168.200.130，应能正常连接
     

   • 在 WinXP 上执行 telnet 192.168.200.130，应无法连接（卡住或超时）
     

实验结果：成功配置防火墙，只允许 Kali 访问 Metasploitable 的 TCP 服务，WinXP 被拒绝访问。

2.2 Snort 入侵检测

操作步骤：

1. 确认 listen.pcap 文件位置：
   之前实验已经把 listen.pcap 文件放入 Kali 中了。
   

2. 运行 Snort 进行检测：

   sudo snort -r /home/kali/listen.pcap -c /etc/snort/snort.lua -A alert_fast -l /var/log/snort
   

   

3. 查看统计信息：
   运行完成后，Snort 会输出数据包统计信息，包括总包数、TCP/UDP 包数、检测到的告警数量等。
   

4. 查看告警日志：

   sudo cat /var/log/snort/alert_fast.txt
   

   
   但是目前因为没有设置规则，所以报警文件为空

2.3 蜜网网关配置分析

由于相关配置分析文件过多，这里只截取部分截图，核心查看代码以及写出，可以自行查阅。
操作步骤：

2. 查看防火墙配置：

   cat /etc/init.d/rc.firewall
   

   

3. 分析防火墙规则：
   蜜网网关的防火墙配置通常包含：

   • 黑名单：阻止已知恶意 IP 的访问
   • 白名单：允许信任 IP 的访问
   • 防护名单：保护特定蜜罐主机不被外部直接访问
   • 数据捕获规则：将特定流量重定向到 Sebek 等数据捕获工具

4. 查看 Snort 配置：

   cat /etc/init.d/snortd
   

   

5. 分析 Snort 规则：
   蜜网网关使用 Snort 作为入侵检测系统，规则文件位于 /etc/snort/rules/ 目录。常见规则包括：

   • 端口扫描检测
   • 特定攻击特征匹配
   • 异常流量检测

6. 查看蜜网网关核心配置文件：

   cat /etc/honeywall.conf
   

   该文件定义了蜜网网关的主要参数，包括网络接口配置、管理 IP、Sebek 配置等。
   

补充配置文件

点击查看代码

###################################################
# This file contains a sample snort configuration. 
# You can take the following steps to create your own custom configuration:
#
#  1) Set the variables for your network
#  2) Configure dynamic loaded libraries
#  3) Configure preprocessors
#  4) Configure output plugins
#  5) Add any runtime config directives
#  6) Customize your rule set
#
###################################################
# Step #1: Set the network variables:
#
# You must change the following variables to reflect your local network. The
# variable is currently setup for an RFC 1918 address space.
#
# You can specify it explicitly as: 
#
# var HOME_NET 10.1.1.0/24
#
# or use global variable $<interfacename>_ADDRESS which will be always
# initialized to IP address and netmask of the network interface which you run
# snort at.  Under Windows, this must be specified as
# $(<interfacename>_ADDRESS), such as:
# $(\Device\Packet_{12345678-90AB-CDEF-1234567890AB}_ADDRESS)
#
# var HOME_NET $eth0_ADDRESS
#
# You can specify lists of IP addresses for HOME_NET
# by separating the IPs with commas like this:
#
# var HOME_NET [10.1.1.0/24,192.168.1.0/24]
#
# MAKE SURE YOU DON'T PLACE ANY SPACES IN YOUR LIST!
#
# or you can specify the variable to be any IP address
# like this:

var HOME_NET any

# Set up the external network addresses as well.  A good start may be "any"
var EXTERNAL_NET any

# Configure your server lists.  This allows snort to only look for attacks to
# systems that have a service up.  Why look for HTTP attacks if you are not
# running a web server?  This allows quick filtering based on IP addresses
# These configurations MUST follow the same configuration scheme as defined
# above for $HOME_NET.  

# List of DNS servers on your network 
var DNS_SERVERS $HOME_NET

# List of SMTP servers on your network
var SMTP_SERVERS $HOME_NET

# List of web servers on your network
var HTTP_SERVERS $HOME_NET

# List of sql servers on your network 
var SQL_SERVERS $HOME_NET

# List of telnet servers on your network
var TELNET_SERVERS $HOME_NET

# List of snmp servers on your network
var SNMP_SERVERS $HOME_NET

# Configure your service ports.  This allows snort to look for attacks destined
# to a specific application only on the ports that application runs on.  For
# example, if you run a web server on port 8081, set your HTTP_PORTS variable
# like this:
#
# var HTTP_PORTS 8081
#
# Port lists must either be continuous [eg 80:8080], or a single port [eg 80].
# We will adding support for a real list of ports in the future.

# Ports you run web servers on
#
# Please note:  [80,8080] does not work.
# If you wish to define multiple HTTP ports, use the following convention
# when customizing your rule set (as part of Step #6 below).  This should
# not be done here, as the rules files may depend on the classifications
# and/or references, which are included below.
# 
## var HTTP_PORTS 80 
## include somefile.rules 
## var HTTP_PORTS 8080
## include somefile.rules 
var HTTP_PORTS 80

# Ports you want to look for SHELLCODE on.
var SHELLCODE_PORTS !80

# Ports you do oracle attacks on
var ORACLE_PORTS 1521

# other variables
# 
# AIM servers.  AOL has a habit of adding new AIM servers, so instead of
# modifying the signatures when they do, we add them to this list of servers.
var AIM_SERVERS [64.12.24.0/23,64.12.28.0/23,64.12.161.0/24,64.12.163.0/24,64.12.200.0/24,205.188.3.0/24,205.188.5.0/24,205.188.7.0/24,205.188.9.0/24,205.188.153.0/24,205.188.179.0/24,205.188.248.0/24]

# Path to your rules files (this can be a relative path)
# Note for Windows users:  You are advised to make this an absolute path,
# such as:  c:\snort\rules
var RULE_PATH /etc/snort/rules

# Configure the snort decoder
# ============================
#
# Snort's decoder will alert on lots of things such as header
# truncation or options of unusual length or infrequently used tcp options
#
#
# Stop generic decode events:
#
# config disable_decode_alerts
#
# Stop Alerts on experimental TCP options
#
# config disable_tcpopt_experimental_alerts
#
# Stop Alerts on obsolete TCP options
#
# config disable_tcpopt_obsolete_alerts
#
# Stop Alerts on T/TCP alerts
#
# In snort 2.0.1 and above, this only alerts when a TCP option is detected
# that shows T/TCP being actively used on the network.  If this is normal
# behavior for your network, disable the next option.
#
# config disable_tcpopt_ttcp_alerts
#
# Stop Alerts on all other TCPOption type events:
#
# config disable_tcpopt_alerts
#
# Stop Alerts on invalid ip options
#
# config disable_ipopt_alerts
#
# Alert if value in length field (IP, TCP, UDP) is greater than the
# actual length of the captured portion of the packet that the length
# is supposed to represent:
#
# config enable_decode_oversized_alerts
#
# Same as above, but drop packet if in Inline mode -
# enable_decode_oversized_alerts must be enabled for this to work:
#
# config enable_decode_oversized_drops
#

# Configure the detection engine
# ===============================
#
# Use a different pattern matcher in case you have a machine with very limited
# resources:
#
# config detection: search-method lowmem

# Configure Inline Resets
# ========================
# 
# If running an iptables firewall with snort in InlineMode() we can now
# perform resets via a physical device. We grab the indev from iptables
# and use this for the interface on which to send resets. This config
# option takes an argument for the src mac address you want to use in the
# reset packet.  This way the bridge can remain stealthy. If the src mac
# option is not set we use the mac address of the indev device. If we
# don't set this option we will default to sending resets via raw socket,
# which needs an ipaddress to be assigned to the int.
#
# config layer2resets: 00:06:76:DD:5F:E3

###################################################
# Step #2: Configure dynamic loaded libraries
#
# If snort was configured to use dynamically loaded libraries,
# those libraries can be loaded here.
#
# Each of the following configuration options can be done via
# the command line as well.
#
# Load all dynamic preprocessors from the install path
# (same as command line option --dynamic-preprocessor-lib-dir)
#
dynamicpreprocessor directory /usr/lib/snort-2.6.1.5_dynamicpreprocessor/
#
# Load a specific dynamic preprocessor library from the install path
# (same as command line option --dynamic-preprocessor-lib)
#
# dynamicpreprocessor file /usr/local/lib/snort_dynamicpreprocessor/libdynamicexample.so
#
# Load a dynamic engine from the install path
# (same as command line option --dynamic-engine-lib)
#
dynamicengine /usr/lib/snort-2.6.1.5_dynamicengine/libsf_engine.so
#
# Load all dynamic rules libraries from the install path
# (same as command line option --dynamic-detection-lib-dir)
#
# dynamicdetection directory /usr/local/lib/snort_dynamicrule/
#
# Load a specific dynamic rule library from the install path
# (same as command line option --dynamic-detection-lib)
#
# dynamicdetection file /usr/local/lib/snort_dynamicrule/libdynamicexamplerule.so
#

###################################################
# Step #3: Configure preprocessors
#
# General configuration for preprocessors is of 
# the form
# preprocessor <name_of_processor>: <configuration_options>

# Configure Flow tracking module
# -------------------------------
#
# The Flow tracking module is meant to start unifying the state keeping
# mechanisms of snort into a single place. Right now, only a portscan detector
# is implemented but in the long term,  many of the stateful subsystems of
# snort will be migrated over to becoming flow plugins. This must be enabled
# for flow-portscan to work correctly.
#
# See README.flow for additional information
#
preprocessor flow: stats_interval 0 hash 2

# frag2: IP defragmentation support
# -------------------------------
# This preprocessor performs IP defragmentation.  This plugin will also detect
# people launching fragmentation attacks (usually DoS) against hosts.  No
# arguments loads the default configuration of the preprocessor, which is a 60
# second timeout and a 4MB fragment buffer. 

# The following (comma delimited) options are available for frag2
#    timeout [seconds] - sets the number of [seconds] that an unfinished 
#                        fragment will be kept around waiting for completion,
#                        if this time expires the fragment will be flushed
#    memcap [bytes] - limit frag2 memory usage to [number] bytes
#                      (default:  4194304)
#
#    min_ttl [number] - minimum ttl to accept
# 
#    ttl_limit [number] - difference of ttl to accept without alerting
#                         will cause false positves with router flap
# 
# Frag2 uses Generator ID 113 and uses the following SIDS 
# for that GID:
#  SID     Event description
# -----   -------------------
#   1       Oversized fragment (reassembled frag > 64k bytes)
#   2       Teardrop-type attack

#preprocessor frag2

# frag3: Target-based IP defragmentation 
# --------------------------------------
#
# Frag3 is a brand new IP defragmentation preprocessor that is capable of
# performing "target-based" processing of IP fragments.  Check out the
# README.frag3 file in the doc directory for more background and configuration
# information.
# 
# Frag3 configuration is a two step process, a global initialization phase 
# followed by the definition of a set of defragmentation engines.  
# 
# Global configuration defines the number of fragmented packets that Snort can
# track at the same time and gives you options regarding the memory cap for the
# subsystem or, optionally, allows you to preallocate all the memory for the 
# entire frag3 system.
#
# frag3_global options:
#   max_frags: Maximum number of frag trackers that may be active at once.  
#              Default value is 8192.
#   memcap: Maximum amount of memory that frag3 may access at any given time.
#           Default value is 4MB.
#   prealloc_frags: Maximum number of individual fragments that may be processed
#                   at once.  This is instead of the memcap system, uses static 
#                   allocation to increase performance.  No default value.  Each
#                   preallocated fragment eats ~1550 bytes.
#
# Target-based behavior is attached to an engine as a "policy" for handling 
# overlaps and retransmissions as enumerated in the Paxson paper.  There are
# currently five policy types available: "BSD", "BSD-right", "First", "Linux" 
# and "Last".  Engines can be bound to standard Snort CIDR blocks or
# IP lists.
#
# frag3_engine options:
#   timeout: Amount of time a fragmented packet may be active before expiring.
#            Default value is 60 seconds.
#   ttl_limit: Limit of delta allowable for TTLs of packets in the fragments. 
#              Based on the initial received fragment TTL.
#   min_ttl: Minimum acceptable TTL for a fragment, frags with TTLs below this
#            value will be discarded.  Default value is 0.
#   detect_anomalies: Activates frag3's anomaly detection mechanisms.
#   policy: Target-based policy to assign to this engine.  Default is BSD.
#   bind_to: IP address set to bind this engine to.  Default is all hosts.
#
# Frag3 configuration example:
#preprocessor frag3_global: max_frags 65536 prealloc_frags 262144
#preprocessor frag3_engine: policy linux \
#                           bind_to [10.1.1.12/32,10.1.1.13/32] \
#                           detect_anomalies
#preprocessor frag3_engine: policy first \
#                           bind_to 10.2.1.0/24 \
#                           detect_anomalies
#preprocessor frag3_engine: policy last \
#                           bind_to 10.3.1.0/24
#preprocessor frag3_engine: policy bsd

preprocessor frag3_global: max_frags 65536
preprocessor frag3_engine: policy first detect_anomalies


# stream4: stateful inspection/stream reassembly for Snort
#----------------------------------------------------------------------
# Use in concert with the -z [all|est] command line switch to defeat stick/snot
# against TCP rules.  Also performs full TCP stream reassembly, stateful
# inspection of TCP streams, etc.  Can statefully detect various portscan
# types, fingerprinting, ECN, etc.

# stateful inspection directive
# no arguments loads the defaults (timeout 30, memcap 8388608)
# options (options are comma delimited):
#   detect_scans - stream4 will detect stealth portscans and generate alerts
#                  when it sees them when this option is set
#   detect_state_problems - detect TCP state problems, this tends to be very
#                           noisy because there are a lot of crappy ip stack
#                           implementations out there
#
#   disable_evasion_alerts - turn off the possibly noisy mitigation of
#                            overlapping sequences.
#
#   ttl_limit [number]     - differential of the initial ttl on a session versus
#                             the normal that someone may be playing games.
#                             Routing flap may cause lots of false positives.
# 
#   keepstats [machine|binary] - keep session statistics, add "machine" to 
#                         get them in a flat format for machine reading, add
#                         "binary" to get them in a unified binary output 
#                         format
#   noinspect - turn off stateful inspection only
#   timeout [number] - set the session timeout counter to [number] seconds,
#                      default is 30 seconds
#   max_sessions [number] - limit the number of sessions stream4 keeps
#                         track of
#   memcap [number] - limit stream4 memory usage to [number] bytes (does
#                     not include session tracking, which is set by the
#                     max_sessions option)
#   log_flushed_streams - if an event is detected on a stream this option will
#                         cause all packets that are stored in the stream4
#                         packet buffers to be flushed to disk.  This only 
#                         works when logging in pcap mode!
#   server_inspect_limit [bytes] - Byte limit on server side inspection.
#   enable_udp_sessions - turn on tracking of "sessions" over UDP.  Requires
#                         configure --enable-stream4udp.  UDP sessions are
#                         only created when there is a rule for the sender or
#                         responder that has a flow or flowbits keyword.
#   max_udp_sessions [number] - limit the number of simultaneous UDP sessions
#                               to track
#   udp_ignore_any - Do not inspect UDP packets unless there is a port specific
#                    rule for a given port.  This is a performance improvement
#                    and turns off inspection for udp xxx any -> xxx any rules
#   cache_clean_sessions [number] - Cleanup the session cache by number sessions
#                                   at a time.  The larger the value, the
#                                   more sessions are purged from the cache when
#                                   the session limit or memcap is reached.
#                                   Defaults to 5.
#   
#   
#
# Stream4 uses Generator ID 111 and uses the following SIDS 
# for that GID:
#  SID     Event description
# -----   -------------------
#   1       Stealth activity
#   2       Evasive RST packet
#   3       Evasive TCP packet retransmission
#   4       TCP Window violation
#   5       Data on SYN packet
#   6       Stealth scan: full XMAS
#   7       Stealth scan: SYN-ACK-PSH-URG
#   8       Stealth scan: FIN scan
#   9       Stealth scan: NULL scan
#   10      Stealth scan: NMAP XMAS scan
#   11      Stealth scan: Vecna scan
#   12      Stealth scan: NMAP fingerprint scan stateful detect
#   13      Stealth scan: SYN-FIN scan
#   14      TCP forward overlap

preprocessor stream4: disable_evasion_alerts

# tcp stream reassembly directive
# no arguments loads the default configuration 
#   Only reassemble the client,
#   Only reassemble the default list of ports (See below),  
#   Give alerts for "bad" streams
#
# Available options (comma delimited):
#   clientonly - reassemble traffic for the client side of a connection only
#   serveronly - reassemble traffic for the server side of a connection only
#   both - reassemble both sides of a session
#   noalerts - turn off alerts from the stream reassembly stage of stream4
#   ports [list] - use the space separated list of ports in [list], "all" 
#                  will turn on reassembly for all ports, "default" will turn
#                  on reassembly for ports 21, 23, 25, 42, 53, 80, 110,
#                  111, 135, 136, 137, 139, 143, 445, 513, 1433, 1521,
#                  and 3306
#   favor_old - favor an old segment (based on sequence number) over a new one.
#               This is the default.
#   favor_new - favor an new segment (based on sequence number) over an old one.
#   overlap_limit [number] - limit on overlaping segments for a session.
#   flush_on_alert - flushes stream when an alert is generated for a session.
#   flush_behavior [mode] -
#           default      - use old static flushpoints (default)
#           large_window - use new larger static flushpoints
#           random       - use random flushpoints defined by flush_base, 
#                          flush_seed and flush_range
#   flush_base [number] - lowest allowed random flushpoint (512 by default)
#   flush_range [number] - number is the space within which random flushpoints
#                          are generated (default 1213)
#   flush_seed [number] - seed for the random number generator, defaults to 
#                         Snort PID + time
#
# Using the default random flushpoints, the smallest flushpoint is 512,
# and the largest is 1725 bytes.
preprocessor stream4_reassemble

# stream5: Target Based stateful inspection/stream reassembly for Snort
# ---------------------------------------------------------------------
# EXPERIMENTAL CODE!!!
#
# THIS CODE IS STILL EXPERIMENTAL AND MAY OR MAY NOT BE STABLE!
# USE AT YOUR OWN RISK!  DO NOT USE IN PRODUCTION ENVIRONMENTS.
# YOU HAVE BEEN WARNED.
#
# Stream5 is a target-based stream engine for Snort.  Its functionality
# replaces that of Stream4.  Consequently, BOTH Stream4 and Stream5
# cannot be used simultaneously.  Comment out the stream4 configurations
# above to use Stream5.
# 
# See README.stream for details on the configuration options.
#
# Example config (that emulates Stream4 with UDP support compiled in)
# preprocessor stream5_global: max_tcp 8192, track_tcp yes, \
#                              track_udp yes
# preprocessor stream5_tcp: policy first, use_static_footprint_sizes
# preprocessor stream5_udp: ignore_any_rules


# Performance Statistics
# ----------------------
# Documentation for this is provided in the Snort Manual.  You should read it.
# It is included in the release distribution as doc/snort_manual.pdf
# 
# preprocessor perfmonitor: time 300 file /var/snort/snort.stats pktcnt 10000

# http_inspect: normalize and detect HTTP traffic and protocol anomalies
#
# lots of options available here. See doc/README.http_inspect.
# unicode.map should be wherever your snort.conf lives, or given
# a full path to where snort can find it.
preprocessor http_inspect: global \
    iis_unicode_map unicode.map 1252 

preprocessor http_inspect_server: server default \
    profile all ports { 80 8080 8180 } oversize_dir_length 500

#
#  Example unique server configuration
#
#preprocessor http_inspect_server: server 1.1.1.1 \
#    ports { 80 3128 8080 } \
#    flow_depth 0 \
#    ascii no \
#    double_decode yes \
#    non_rfc_char { 0x00 } \
#    chunk_length 500000 \
#    non_strict \
#    oversize_dir_length 300 \
#    no_alerts


# rpc_decode: normalize RPC traffic
# ---------------------------------
# RPC may be sent in alternate encodings besides the usual 4-byte encoding
# that is used by default. This plugin takes the port numbers that RPC
# services are running on as arguments - it is assumed that the given ports
# are actually running this type of service. If not, change the ports or turn
# it off.
# The RPC decode preprocessor uses generator ID 106
#
# arguments: space separated list
# alert_fragments - alert on any rpc fragmented TCP data
# no_alert_multiple_requests - don't alert when >1 rpc query is in a packet
# no_alert_large_fragments - don't alert when the fragmented
#                            sizes exceed the current packet size
# no_alert_incomplete - don't alert when a single segment
#                       exceeds the current packet size

preprocessor rpc_decode: 111 32771

# bo: Back Orifice detector
# -------------------------
# Detects Back Orifice traffic on the network.
#
# arguments:  
#   syntax:
#     preprocessor bo: noalert { client | server | general | snort_attack } \
#                      drop    { client | server | general | snort_attack }
#   example:
#     preprocessor bo: noalert { general server } drop { snort_attack }

# 
# The Back Orifice detector uses Generator ID 105 and uses the 
# following SIDS for that GID:
#  SID     Event description
# -----   -------------------
#   1       Back Orifice traffic detected
#   2       Back Orifice Client Traffic Detected
#   3       Back Orifice Server Traffic Detected
#   4       Back Orifice Snort Buffer Attack

preprocessor bo

# telnet_decode: Telnet negotiation string normalizer
# ---------------------------------------------------
# This preprocessor "normalizes" telnet negotiation strings from telnet and ftp
# traffic.  It works in much the same way as the http_decode preprocessor,
# searching for traffic that breaks up the normal data stream of a protocol and
# replacing it with a normalized representation of that traffic so that the
# "content" pattern matching keyword can work without requiring modifications.
# This preprocessor requires no arguments.
#
# DEPRECATED in favor of ftp_telnet dynamic preprocessor
#preprocessor telnet_decode
#
# ftp_telnet: FTP & Telnet normalizer, protocol enforcement and buff overflow
# ---------------------------------------------------------------------------
# This preprocessor normalizes telnet negotiation strings from telnet and
# ftp traffic.  It looks for traffic that breaks the normal data stream
# of the protocol, replacing it with a normalized representation of that
# traffic so that the "content" pattern matching keyword can work without
# requiring modifications.
#
# It also performs protocol correctness checks for the FTP command channel,
# and identifies open FTP data transfers.
#
# FTPTelnet has numerous options available, please read
# README.ftptelnet for help configuring the options for the global
# telnet, ftp server, and ftp client sections for the protocol.

#####
# Per Step #2, set the following to load the ftptelnet preprocessor
# dynamicpreprocessor <full path to libsf_ftptelnet_preproc.so>
# or use commandline option
# --dynamic-preprocessor-lib <full path to libsf_ftptelnet_preproc.so>

preprocessor ftp_telnet: global \
   encrypted_traffic yes \
   inspection_type stateful

preprocessor ftp_telnet_protocol: telnet \
   normalize \
   ayt_attack_thresh 200

# This is consistent with the FTP rules as of 18 Sept 2004.
# CWD can have param length of 200
# MODE has an additional mode of Z (compressed)
# Check for string formats in USER & PASS commands
# Check nDTM commands that set modification time on the file.
preprocessor ftp_telnet_protocol: ftp server default \
   def_max_param_len 100 \
   alt_max_param_len 200 { CWD } \
   cmd_validity MODE < char ASBCZ > \
   cmd_validity MDTM < [ date nnnnnnnnnnnnnn[.n[n[n]]] ] string > \
   chk_str_fmt { USER PASS RNFR RNTO SITE MKD } \
   telnet_cmds yes \
   data_chan

preprocessor ftp_telnet_protocol: ftp client default \
   max_resp_len 256 \
   bounce yes \
   telnet_cmds yes

# smtp: SMTP normalizer, protocol enforcement and buffer overflow
# ---------------------------------------------------------------------------
# This preprocessor normalizes SMTP commands by removing extraneous spaces.
# It looks for overly long command lines, response lines, and data header lines.
# It can alert on invalid commands, or specific valid commands.  It can optionally
# ignore mail data, and can ignore TLS encrypted data.
#
# SMTP has numerous options available, please read README.SMTP for help
# configuring options.

#####
# Per Step #2, set the following to load the smtp preprocessor
# dynamicpreprocessor <full path to libsf_smtp_preproc.so>
# or use commandline option
# --dynamic-preprocessor-lib <full path to libsf_smtp_preproc.so>

preprocessor smtp: \
  ports { 25 } \
  inspection_type stateful \
  normalize cmds \
  normalize_cmds { EXPN VRFY RCPT } \
  alt_max_command_line_len 260 { MAIL } \
  alt_max_command_line_len 300 { RCPT } \
  alt_max_command_line_len 500 { HELP HELO ETRN } \
  alt_max_command_line_len 255 { EXPN VRFY }

# sfPortscan
# ----------
# Portscan detection module.  Detects various types of portscans and
# portsweeps.  For more information on detection philosophy, alert types,
# and detailed portscan information, please refer to the README.sfportscan.
#
# -configuration options-
#     proto { tcp udp icmp ip all }
#       The arguments to the proto option are the types of protocol scans that
#       the user wants to detect.  Arguments should be separated by spaces and
#       not commas.
#     scan_type { portscan portsweep decoy_portscan distributed_portscan all }
#       The arguments to the scan_type option are the scan types that the
#       user wants to detect.  Arguments should be separated by spaces and not
#       commas.
#     sense_level { low|medium|high }
#       There is only one argument to this option and it is the level of
#       sensitivity in which to detect portscans.  The 'low' sensitivity
#       detects scans by the common method of looking for response errors, such
#       as TCP RSTs or ICMP unreachables.  This level requires the least
#       tuning.  The 'medium' sensitivity level detects portscans and 
#       filtered portscans (portscans that receive no response).  This
#       sensitivity level usually requires tuning out scan events from NATed
#       IPs, DNS cache servers, etc.  The 'high' sensitivity level has
#       lower thresholds for portscan detection and a longer time window than
#       the 'medium' sensitivity level.  Requires more tuning and may be noisy
#       on very active networks.  However, this sensitivity levels catches the
#       most scans.
#     memcap { positive integer }
#       The maximum number of bytes to allocate for portscan detection.  The
#       higher this number the more nodes that can be tracked.
#     logfile { filename }
#       This option specifies the file to log portscan and detailed portscan
#       values to.  If there is not a leading /, then snort logs to the
#       configured log directory.  Refer to README.sfportscan for details on
#       the logged values in the logfile.
#     watch_ip { Snort IP List }
#     ignore_scanners { Snort IP List }
#     ignore_scanned { Snort IP List }
#       These options take a snort IP list as the argument.  The 'watch_ip'
#       option specifies the IP(s) to watch for portscan.  The 
#       'ignore_scanners' option specifies the IP(s) to ignore as scanners.
#       Note that these hosts are still watched as scanned hosts.  The
#       'ignore_scanners' option is used to tune alerts from very active
#       hosts such as NAT, nessus hosts, etc.  The 'ignore_scanned' option 
#       specifies the IP(s) to ignore as scanned hosts.  Note that these hosts
#       are still watched as scanner hosts.  The 'ignore_scanned' option is
#       used to tune alerts from very active hosts such as syslog servers, etc.
#     detect_ack_scans
#       This option will include sessions picked up in midstream by the stream
#       module, which is necessary to detect ACK scans.  However, this can lead to
#       false alerts, especially under heavy load with dropped packets; which is why
#       the option is off by default.
#
preprocessor sfportscan: proto  { all } \
                         memcap { 10000000 } \
                         sense_level { low }

# arpspoof
#----------------------------------------
# Experimental ARP detection code from Jeff Nathan, detects ARP attacks,
# unicast ARP requests, and specific ARP mapping monitoring.  To make use of
# this preprocessor you must specify the IP and hardware address of hosts on
# the same layer 2 segment as you.  Specify one host IP MAC combo per line.
# Also takes a "-unicast" option to turn on unicast ARP request detection. 
# Arpspoof uses Generator ID 112 and uses the following SIDS for that GID:

#  SID     Event description
# -----   -------------------
#   1       Unicast ARP request
#   2       Etherframe ARP mismatch (src)
#   3       Etherframe ARP mismatch (dst)
#   4       ARP cache overwrite attack

#preprocessor arpspoof
#preprocessor arpspoof_detect_host: 192.168.40.1 f0:0f:00:f0:0f:00

# ssh
#----------------------------------------
# EXPERIMENTAL CODE!!!
#
# THIS CODE IS STILL EXPERIMENTAL AND MAY OR MAY NOT BE STABLE!
# USE AT YOUR OWN RISK!  DO NOT USE IN PRODUCTION ENVIRONMENTS.
# YOU HAVE BEEN WARNED.
#
# The SSH preprocessor detects the following exploits: Gobbles, CRC 32,
# Secure CRT, and the Protocol Mismatch exploit.
#
# Both Gobbles and CRC 32 attacks occur after the key exchange, and are
# therefore encrypted.  Both attacks involve sending a large payload
# (20kb+) to the server immediately after the authentication challenge.
# To detect the attacks, the SSH preprocessor counts the number of bytes
# transmitted to the server.  If those bytes exceed a pre-defined limit
# within a pre-define number of packets, an alert is generated.  Since
# Gobbles only effects SSHv2 and CRC 32 only effects SSHv1, the SSH
# version string exchange is used to distinguish the attacks.
#
# The Secure CRT and protocol mismatch exploits are observable before
# the key exchange.
#
# SSH has numerous options available, please read README.ssh for help
# configuring options.

#####
# Per Step #2, set the following to load the ssh preprocessor
# dynamicpreprocessor <full path to libsf_ssh_preproc.so>
# or use commandline option
# --dynamic-preprocessor-lib <full path to libsf_ssh_preproc.so>
#
#preprocessor ssh: server_ports { 22 } \
#                  max_client_bytes 19600 \
#                  max_encrypted_packets 20

# DCE/RPC
#----------------------------------------
#
# The dcerpc preprocessor detects and decodes SMB and DCE/RPC traffic.
# It is primarily interested in DCE/RPC data, and only decodes SMB
# to get at the DCE/RPC data carried by the SMB layer.
# 
# Currently, the preprocessor only handles reassembly of fragmentation
# at both the SMB and DCE/RPC layer.  Snort rules can be evaded by
# using both types of fragmentation; with the preprocessor enabled
# the rules are given a buffer with a reassembled SMB or DCE/RPC
# packet to examine.
# 
# At the SMB layer, only fragmentation using WriteAndX is currently
# reassembled.  Other methods will be handled in future versions of
# the preprocessor.
# 
# Autodetection of SMB is done by looking for "\xFFSMB" at the start of
# the SMB data, as well as checking the NetBIOS header (which is always
# present for SMB) for the type "SMB Session".
# 
# Autodetection of DCE/RPC is not as reliable.  Currently, two bytes are
# checked in the packet.  Assuming that the data is a DCE/RPC header,
# one byte is checked for DCE/RPC version (5) and another for the type
# "DCE/RPC Request".  If both match, the preprocessor proceeds with that
# assumption that it is looking at DCE/RPC data.  If subsequent checks
# are nonsensical, it ends processing.
#
# DCERPC has numerous options available, please read README.dcerpc for help
# configuring options.

#####
# Per Step #2, set the following to load the dcerpc preprocessor
# dynamicpreprocessor <full path to libsf_dcerpc_preproc.so>
# or use commandline option
# --dynamic-preprocessor-lib <full path to libsf_dcerpc_preproc.so>

preprocessor dcerpc: \
    autodetect \
    max_frag_size 3000 \
    memcap 100000

# DNS
#----------------------------------------
# The dns preprocessor (currently) decodes DNS Response traffic
# and detects a few vulnerabilities.
#
# DNS has a few options available, please read README.dns for
# help configuring options.

#####
# Per Step #2, set the following to load the dns preprocessor
# dynamicpreprocessor <full path to libsf_dns_preproc.so>
# or use commandline option
# --dynamic-preprocessor-lib <full path to libsf_dns_preproc.so>

preprocessor dns: \
    ports { 53 } \
    enable_rdata_overflow

####################################################################
# Step #4: Configure output plugins
#
# Uncomment and configure the output plugins you decide to use.  General
# configuration for output plugins is of the form:
#
# output <name_of_plugin>: <configuration_options>
#
# alert_syslog: log alerts to syslog
# ----------------------------------
# Use one or more syslog facilities as arguments.  Win32 can also optionally
# specify a particular hostname/port.  Under Win32, the default hostname is
# '127.0.0.1', and the default port is 514.
#
# [Unix flavours should use this format...]
# output alert_syslog: LOG_AUTH LOG_ALERT
#
# [Win32 can use any of these formats...]
# output alert_syslog: LOG_AUTH LOG_ALERT
# output alert_syslog: host=hostname, LOG_AUTH LOG_ALERT
# output alert_syslog: host=hostname:port, LOG_AUTH LOG_ALERT

# log_tcpdump: log packets in binary tcpdump format
# -------------------------------------------------
# The only argument is the output file name.
#
# output log_tcpdump: tcpdump.log

# database: log to a variety of databases
# ---------------------------------------
# See the README.database file for more information about configuring
# and using this plugin.
#
# output database: log, mysql, user=root password=test dbname=db host=localhost
# output database: alert, postgresql, user=snort dbname=snort
# output database: log, odbc, user=snort dbname=snort
# output database: log, mssql, dbname=snort user=snort password=test
# output database: log, oracle, dbname=snort user=snort password=test

# unified: Snort unified binary format alerting and logging
# -------------------------------------------------------------
# The unified output plugin provides two new formats for logging and generating
# alerts from Snort, the "unified" format.  The unified format is a straight
# binary format for logging data out of Snort that is designed to be fast and
# efficient.  Used with barnyard (the new alert/log processor), most of the
# overhead for logging and alerting to various slow storage mechanisms such as
# databases or the network can now be avoided.  
#
# Check out the spo_unified.h file for the data formats.
#
# Two arguments are supported.
#    filename - base filename to write to (current time_t is appended)
#    limit    - maximum size of spool file in MB (default: 128)
#
# output alert_unified: filename snort.alert, limit 128
# output log_unified: filename snort.log, limit 128


# prelude: log to the Prelude Hybrid IDS system
# ---------------------------------------------
#
# profile = Name of the Prelude profile to use (default is snort).
#
# Snort priority to IDMEF severity mappings:
# high < medium < low < info
#
# These are the default mapped from classification.config:
# info   = 4
# low    = 3
# medium = 2
# high   = anything below medium
#
# output alert_prelude
# output alert_prelude: profile=snort-profile-name


# You can optionally define new rule types and associate one or more output
# plugins specifically to that type.
#
# This example will create a type that will log to just tcpdump.
# ruletype suspicious
# {
#   type log
#   output log_tcpdump: suspicious.log
# }
#
# EXAMPLE RULE FOR SUSPICIOUS RULETYPE:
# suspicious tcp $HOME_NET any -> $HOME_NET 6667 (msg:"Internal IRC Server";)
#
# This example will create a rule type that will log to syslog and a mysql
# database:
# ruletype redalert
# {
#   type alert
#   output alert_syslog: LOG_AUTH LOG_ALERT
#   output database: log, mysql, user=snort dbname=snort host=localhost
# }
#
# EXAMPLE RULE FOR REDALERT RULETYPE:
# redalert tcp $HOME_NET any -> $EXTERNAL_NET 31337 \
#   (msg:"Someone is being LEET"; flags:A+;)

#
# Include classification & priority settings
# Note for Windows users:  You are advised to make this an absolute path,
# such as:  c:\snort\etc\classification.config
#

include classification.config

#
# Include reference systems
# Note for Windows users:  You are advised to make this an absolute path,
# such as:  c:\snort\etc\reference.config
#

include reference.config

####################################################################
# Step #5: Configure snort with config statements
#
# See the snort manual for a full set of configuration references
#
# config flowbits_size: 64
#
# New global ignore_ports config option from Andy Mullican
#
# config ignore_ports: <tcp|udp> <list of ports separated by whitespace>
# config ignore_ports: tcp 21 6667:6671 1356
# config ignore_ports: udp 1:17 53


####################################################################
# Step #6: Customize your rule set
#
# Up to date snort rules are available at http://www.snort.org
#
# The snort web site has documentation about how to write your own custom snort
# rules.

#=========================================
# Include all relevant rulesets here 
# 
# The following rulesets are disabled by default:
#
#   web-attacks, backdoor, shellcode, policy, porn, info, icmp-info, virus,
#   chat, multimedia, and p2p
#            
# These rules are either site policy specific or require tuning in order to not
# generate false positive alerts in most enviornments.
# 
# Please read the specific include file for more information and
# README.alert_order for how rule ordering affects how alerts are triggered.
#=========================================

include $RULE_PATH/local.rules
include $RULE_PATH/bad-traffic.rules
include $RULE_PATH/exploit.rules
include $RULE_PATH/scan.rules
include $RULE_PATH/finger.rules
include $RULE_PATH/ftp.rules
include $RULE_PATH/telnet.rules
include $RULE_PATH/rpc.rules
include $RULE_PATH/rservices.rules
include $RULE_PATH/dos.rules
include $RULE_PATH/ddos.rules
include $RULE_PATH/dns.rules
include $RULE_PATH/tftp.rules

include $RULE_PATH/web-cgi.rules
include $RULE_PATH/web-coldfusion.rules
include $RULE_PATH/web-iis.rules
include $RULE_PATH/web-frontpage.rules
include $RULE_PATH/web-misc.rules
include $RULE_PATH/web-client.rules
include $RULE_PATH/web-php.rules

include $RULE_PATH/sql.rules
include $RULE_PATH/x11.rules
include $RULE_PATH/icmp.rules
include $RULE_PATH/netbios.rules
include $RULE_PATH/misc.rules
include $RULE_PATH/attack-responses.rules
include $RULE_PATH/oracle.rules
include $RULE_PATH/mysql.rules
include $RULE_PATH/snmp.rules

include $RULE_PATH/smtp.rules
include $RULE_PATH/imap.rules
include $RULE_PATH/pop2.rules
include $RULE_PATH/pop3.rules

include $RULE_PATH/nntp.rules
include $RULE_PATH/other-ids.rules
# include $RULE_PATH/web-attacks.rules
# include $RULE_PATH/backdoor.rules
# include $RULE_PATH/shellcode.rules
# include $RULE_PATH/policy.rules
# include $RULE_PATH/porn.rules
# include $RULE_PATH/info.rules
# include $RULE_PATH/icmp-info.rules
# include $RULE_PATH/virus.rules
# include $RULE_PATH/chat.rules
# include $RULE_PATH/multimedia.rules
# include $RULE_PATH/p2p.rules
# include $RULE_PATH/spyware-put.rules
include $RULE_PATH/experimental.rules

# Include any thresholding or suppression commands. See threshold.conf in the
# <snort src>/etc directory for details. Commands don't necessarily need to be
# contained in this conf, but a separate conf makes it easier to maintain them. 
# Note for Windows users:  You are advised to make this an absolute path,
# such as:  c:\snort\etc\threshold.conf
# Uncomment if needed.
# include threshold.conf

蜜网网关工作原理分析：

蜜网网关通过以下方式实现攻击数据捕获和控制：

1. 透明网桥模式：蜜网网关以透明网桥方式部署在攻击网段（VMnet8）和靶机网段（VMnet1）之间，所有流量必须经过它。

2. iptables 流量控制：通过 iptables 规则对进出蜜网的流量进行精细控制，包括：

   • 限制出站连接次数（防止攻击者用靶机发起 DoS 攻击）
   • 标记可疑流量用于分析
   • 实现数据捕获的流量重定向

3. Snort IDS 检测：Snort 实时分析经过的流量，根据规则匹配检测攻击行为：

   • 端口扫描检测（如 Nmap SYN 扫描）
   • 漏洞利用尝试检测
   • 异常协议行为检测

4. Sebek 数据捕获：在靶机内核中植入 Sebek 模块，捕获攻击者的所有操作（击键、文件访问等），通过隐蔽通道发送给蜜网网关。

5. Walleye 管理界面：通过 Web 界面（https://192.168.200.8）查看捕获的攻击数据、流量统计和 Snort 告警。

3. 学习中遇到的问题及解决

• 问题1：在 Metasploitable 上执行 iptables -P INPUT DROP 后，SSH 连接立即断开，无法再远程管理
  解决方案：配置防火墙时应先添加允许 SSH 的规则，再设置默认策略为 DROP。正确顺序应该是：

  iptables -A INPUT -p tcp --dport 22 -j ACCEPT
  iptables -P INPUT DROP
  

  如果已被锁定，需通过 VMware 控制台本地登录恢复。

• 问题2：输入apt install snort后，命令无法正常执行，因为apt版本落后
  解决方案：更新apt，输入apt update

• 问题3：蜜网网关中无法查看 iptables 规则（权限不足）
  解决方案：使用 su - 切换到 root 用户后再执行。

4. 实践总结

在实验四的攻击实验中，当时就有意识的提前了解防火墙技术，这次实验也刚好学习了相关防火墙配置、入侵检测系统（Snort）的使用以及蜜网网关的防护机制分析等相关知识。

通过本次实验，我主要有以下三点收获：

一是防火墙的访问控制作用：iptables 作为 Linux 系统的核心防火墙工具，能够对 IP 地址、端口、协议等条件对网络流量进行精细控制。实验通过配置 ICMP 过滤和 IP 白名单，让我直观理解了防火墙如何实现指定拦截的操作。

二是Snort入侵检测的能力：Snort 作为开源 IDS/IPS 系统，能够从 pcap 文件中读取流量并基于规则进行检测，并可以看到各种报警信息。

三是蜜网网关的综合防护：蜜网网关将防火墙（iptables）和入侵检测（Snort）技术有机结合，实现了攻击数据捕获与控制的双重目标。防火墙负责流量控制和隔离，IDS 负责攻击检测和告警，两者协同工作，既保护了真实的靶机环境，又为安全分析提供了完整的攻击数据。