Internet Relay Chat (IRC)

How IRC Works as a Security-Relevant Protocol

IRC is a lightweight, text-based protocol built for real-time channel communication. Its simplicity made it popular long before modern collaboration platforms, and that same simplicity is what can make it attractive in hostile environments: traffic is easy to script, easy to automate and often easy to blend into routine network noise.

Because IRC is a protocol rather than a single product, the security posture depends heavily on where it is permitted, how it is monitored and whether legacy clients or relays are still present. For defenders, the key question is not whether IRC exists on the network, but whether its use is expected and controlled.

Why IRC Still Matters in Modern Defences

IRC remains relevant because older command-and-control tradecraft still values simplicity, low overhead and broad compatibility. Attackers can use it for coordination, status updates and lightweight data exchange, particularly in environments where legacy protocols are less scrutinised than web traffic or cloud services.

The protocol’s long history also means it can appear in forgotten corners of an environment, including old tooling, embedded systems and inherited workflows. That creates a blind spot: a channel may be technically legitimate while still providing a convenient path for abuse if it is not tied to a clearly owned business use case.

Protocol governance matters here. Standards and registry bodies such as the IETF and IANA are part of the broader internet infrastructure ecosystem, but operational safety depends on what your own estate allows, logs and alerts on.

Exposure, Monitoring and Detection

Exposure usually shows up first as unexpected outbound connections, especially to hosts that should not be running chat relay services. Unusual channel names, repeated joins and parts, or clients that do not fit normal workstation baselines can all indicate misuse. Legacy IRC clients are particularly important because they may bypass modern proxying, TLS inspection or endpoint policies.

Detection should focus on network telemetry and behaviour, not only on port numbers. Defenders should look for repeated IRC-style session patterns, long-lived connections, command bursts and internal systems that initiate communication to a small set of external relays. Where access control and logging are mature, those signals are easier to separate from historical or approved use. A general control baseline such as NIST SP 800-53 Rev 5 Security and Privacy Controls helps anchor monitoring, logging and boundary protection expectations.

From a threat-analysis perspective, IRC is best understood as a low-friction communication layer that can support persistence, coordination and limited exfiltration. It is not inherently malicious, but it is easy to repurpose when defenders do not have protocol-level visibility.

Hardening and Response When IRC Is Present

Where IRC is not a required business protocol, the safest posture is to restrict or segment it so that only explicitly owned systems can use it. If it must exist, treat it as an exception requiring documented ownership, logging and review. Security teams should also watch for toolchains or endpoints that still rely on obsolete clients, because old software can preserve an attack path even after the original use case has disappeared.

When suspicious IRC activity is found, responders should determine whether it is simply a legacy application, a misconfiguration or a sign of active command-and-control. If compromise is confirmed, contain the affected host, review outbound connections and assess whether any channels, nicknames, relay addresses or local client settings need to be removed before the system returns to service. Baseline network defence patterns in NIST Cybersecurity Framework 2.0 and adversary tradecraft mapping in MITRE ATT&CK Enterprise Matrix are both useful when turning an IRC observation into a broader hunt.

Failure mechanism: IRC becomes dangerous when an organisation fails to distinguish sanctioned legacy usage from covert outbound command traffic, allowing a simple text channel to evade ordinary scrutiny.

Impact: The result can be persistent remote control, low-visibility coordination between systems, and delayed detection of lateral movement or data exchange.

Practitioner Guidance

What to watch for: The practical signal is any IRC activity that lacks an obvious owner, ticket or business justification. If you cannot name the service, user population or system purpose behind the traffic, treat it as a review item rather than a harmless legacy protocol.

Governance implication: IRC should sit in the same ownership model as other legacy protocols and remote administration paths. That means assigning an approver, documenting the exception and deciding whether the protocol is still needed at all. For network teams, the most useful control is usually not deeper inspection, but a clear decision on whether the protocol is permitted in the first place.

Related resources from NHI Mgmt Group

• How should security teams respond when malicious IDE extensions can relay chat history and pasted code to external services?
• Why are secrets in logs and chat tools so dangerous?
• How should security teams reduce NTLM relay risk in Active Directory?
• When should organisations prioritise relay and coercion controls?