Communications over IRC network

Hunt Hypothesis

Adversaries may use IRC networks to exfiltrate data or establish command and control channels, leveraging the protocol’s anonymity and persistence capabilities. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify potential covert communication channels and mitigate advanced persistent threat activities.

YARA Rule

rule network_irc {
    meta:
        author = "x0r"
        description = "Communications over IRC network"
	version = "0.1"
    strings:
        $s1 = "NICK"
        $s2 = "PING"
        $s3 = "JOIN"
        $s4 = "USER"
        $s5 = "PRIVMSG"
    condition:
        all of them
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 5 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: System administration using IRC for internal communication
  Description: An admin uses an IRC client like irssi or WeeChat to communicate with other team members during shift handover or incident response.
  Filter/Exclusion: Exclude traffic from known admin workstations or users with admin privileges using a src_ip or user_agent filter.

• Scenario: Scheduled job status updates via IRC
  Description: A cron job or scheduled task uses ircbot or node-irc to send status updates to an IRC channel for monitoring purposes.
  Filter/Exclusion: Exclude traffic from known job servers or processes using process_name or destination_port (e.g., 6667).

• Scenario: Internal IRC server used for team collaboration
  Description: The organization uses an internal IRC server (e.g., ircd-hybrid) for team collaboration, and legitimate traffic is being flagged.
  Filter/Exclusion: Exclude traffic to internal IRC servers using dest_ip or dest_port (e.g., 6667) that are known to be internal.

• Scenario: IRC-based chat application for customer support
  Description: A customer support team uses an IRC-based chat tool like ChatZilla or IRC-based chatbot to handle support queries.
  Filter/Exclusion: Exclude traffic from the support team’s IP range or user group using src_ip or user_group.

• Scenario: IRC used for logging or monitoring purposes
  Description: A monitoring tool like Nagios or Zabbix uses IRC to send alerts or logs to an IRC channel.
  Filter/Exclusion: Exclude traffic from monitoring tools using process_name or destination_port (e.g., 6667)