如何用Wireshark分析PCAP查找IRC JOIN命令？关联Snort规则sid:2000348

Great question! Let's walk through each part of your problem step by step, since you're dealing with non-standard IRC traffic over port 443 flagged by Snort rule sid:2000348.

1. How to Find the IRC JOIN Command in Your PCAP #

Since this IRC traffic is using port 443 (usually reserved for HTTPS), Wireshark won't automatically recognize it as IRC by default. Here's what to do:

• First, narrow down the traffic with a basic filter: tcp.port == 443 to focus on all packets using that port.
• Next, tell Wireshark to decode this port as IRC:
  1. Right-click any packet in the filtered list that belongs to the suspicious flow.
  2. Select Decode As from the menu.
  3. In the "Current" column, find the entry for port 443, then use the dropdown to select IRC as the protocol. Click OK.
• Now you can use a precise IRC filter to find JOIN commands: irc.command == JOIN. This will show only packets where the IRC command is JOIN, making it easy to isolate the traffic in question.

2. Can You Search for the String "JOIN" Across the Entire PCAP? #

Absolutely! Wireshark has a built-in search function that lets you scan every packet for specific strings:

• Press Ctrl+F (or go to Edit > Find Packet) to open the search bar.
• In the search options:
  • Set the Search In dropdown to Entire Capture (instead of just the displayed packets).
  • Choose String as the search type.
  • Enter "JOIN" in the search field.
  • Optionally, select Packet Bytes to search the raw payload, or Packet Details to look within decoded protocol fields.
• Click Find Next or Find Previous to jump to each occurrence of the string. Just note that if the traffic was encrypted (unlikely for malicious IRC over 443, but possible), this search won't find anything— but since the Snort rule flagged it, it's almost certainly plaintext.

3. Does Wireshark Support the PCRE from the Snort Rule? #

Yes, Wireshark supports Perl-compatible regular expressions (PCRE) in its display filters, though there's a small syntax adjustment needed from the Snort rule. The Snort rule uses pcre:"/&|#|+|!/R"— here's how to translate that for Wireshark:

• Wireshark uses the matches keyword to apply regex filters. You'll need to escape the + character (since it's a special regex quantifier) with a backslash (so \+).
• A working filter would look like this:

  tcp.port == 443 and frame matches "&|#|\\+|!"
  

• If you want to combine this with the IRC JOIN command filter to be even more precise:

  irc.command == JOIN and frame matches "&|#|\\+|!"
  

This will isolate exactly the packets that match both the JOIN command and the special characters flagged by the Snort rule.

内容的提问来源于stack exchange，提问作者Heisenberg