How to remediate – BNC Detection

1. Introduction

BNC Detection indicates that an IRC bouncer is running on a port within your network. An IRC bouncer allows persistent connections to IRC servers, often used by attackers to maintain control of botnets and avoid detection. This affects systems running IRC clients or those unintentionally hosting bouncers. A successful compromise could lead to loss of confidentiality, integrity, and availability through remote control of affected systems.

2. Technical Explanation

BNC (Bounce Network Connector) is an IRC bouncer that proxies communications between IRC clients and servers. Attackers install BNCs on compromised hosts to create a hidden command-and-control channel for botnets, allowing them to issue commands remotely even if the original host’s network connection changes. The vulnerability lies in the unexpected presence of this software, which is rarely used legitimately.

• Root cause: Unauthorised or unknown IRC bouncer software running on a system.
• Exploit mechanism: An attacker installs BNC to control compromised systems remotely via an IRC network. They can then use the botnet for malicious activities like DDoS attacks, spam distribution, and data theft.
• Scope: Any system capable of running an IRC bouncer (typically Linux or Windows servers).

3. Detection and Assessment

Confirming a BNC presence involves checking listening ports and identifying the software version. A thorough assessment includes network traffic analysis for IRC-related communications.

• Quick checks: Use netstat -tulnp (Linux) or netstat -ano | findstr "LISTENING" (Windows) to identify processes listening on unusual ports, specifically those associated with IRC (typically 6667, 7000).
• Scanning: Nessus plugin ID 32981 can detect BNC services. This is an example only and may require updating.
• Logs and evidence: Check system logs for processes named ‘bnc’ or related IRC client software. Examine firewall logs for connections to known IRC servers.

netstat -tulnp | grep bnc

4. Solution / Remediation Steps

Remediating BNC detection requires verifying legitimate use and removing the software if unauthorized. Follow these steps carefully to avoid disrupting legitimate services.

4.1 Preparation

• Ensure you have appropriate permissions to remove software and modify configurations. A rollback plan involves restoring from the pre-change snapshot.
• Change windows should be scheduled during off-peak hours with approval from the security team.

4.2 Implementation

1. Step 1: Verify if the BNC installation is authorized by checking with system owners or application administrators.
2. Step 2: If unauthorized, identify the process ID (PID) of the BNC using ps aux | grep bnc (Linux) or Task Manager (Windows).
3. Step 3: Terminate the BNC process using kill (Linux) or Task Manager (Windows).
4. Step 4: Remove the BNC software and associated files from the system. Use package managers if available (e.g., apt remove bnc, yum remove bnc).

4.3 Config or Code Example

Before

#Example configuration file showing BNC settings (example only)
listen 0.0.0.0:6667
channels #yourchannel

After

#Configuration file should be empty or contain no IRC bouncer related entries after removal.

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent BNC installations and detect malicious activity. These include least privilege, regular system audits, and intrusion detection systems.

• Practice 1: Least privilege – limit user accounts’ permissions to reduce the impact if a system is compromised and used to install unwanted software.
• Practice 2: Regular system audits – routinely check for unexpected software installations or running processes on critical servers.

4.5 Automation (Optional)

#!/bin/bash
# Example script to check for running BNC processes (Linux)
ps aux | grep bnc > /tmp/bnc_output.txt
if grep -q "bnc" /tmp/bnc_output.txt; then
  echo "BNC process found, investigate immediately!"
fi

5. Verification / Validation

Confirm the fix by verifying that the BNC process is no longer running and network connections to IRC servers are blocked. Perform a smoke test of essential system functions.

• Post-fix check: Run netstat -tulnp | grep bnc (Linux) or netstat -ano | findstr "LISTENING" (Windows). Expected output should be empty.
• Re-test: Re-run the initial scan using netstat to confirm no BNC processes are listening on IRC ports.
• Monitoring: Monitor firewall logs for any new connections to known IRC server IP addresses or ports.

netstat -tulnp | grep bnc

6. Preventive Measures and Monitoring

Preventive measures include establishing security baselines, implementing intrusion detection systems, and maintaining a robust patch management process. For example, regularly update system configurations to adhere to CIS benchmarks.

• Baselines: Update your security baseline or policy to explicitly prohibit unauthorized IRC software installations.
• Asset and patch process: Implement a regular review cycle for system configurations and installed software, ensuring timely patching of vulnerabilities.

7. Risks, Side Effects, and Roll Back

• Roll back: Restore the system from the pre-change snapshot to revert any modifications made during remediation.

8. References and Resources

• Vendor advisory or bulletin: http://www.gotbnc.com/
• NVD or CVE entry: No specific CVE is associated with the mere presence of BNC software, but related exploits exist for compromised systems.
• Product or platform documentation relevant to the fix: https://en.wikipedia.org/wiki/Bouncer_(networking)