How to remediate – Anon Proxy Server Software Detection

1. Introduction

Anon Proxy Server is a proxy server software that can act as an HTTP, HTTPS, or Socks proxy, and also supports P2P anonymous proxy operation. Its presence on a network may indicate unintended data exposure or policy violations. This vulnerability affects systems running the Anon Proxy Server service. A successful compromise could lead to information disclosure, unauthorized access, or man-in-the-middle attacks. Confidentiality, integrity, and availability may be impacted.

2. Technical Explanation

Anon Proxy Server runs as a network service listening for proxy requests. The software itself is not inherently vulnerable but its operation can create security risks if not properly secured or monitored. Attackers could exploit the server to intercept and modify traffic, potentially gaining access to sensitive data. Preconditions include network connectivity to the affected port and the server being configured in a way that allows unauthorized access.

• Root cause: The service is running without sufficient security controls.
• Exploit mechanism: An attacker could connect to the proxy server and intercept traffic passing through it, or use it as a relay for malicious activity.
• Scope: Affected platforms are those running Anon Proxy Server software (Windows, Linux, macOS).

3. Detection and Assessment

To confirm whether a system is vulnerable, first check if the service is listening on standard proxy ports. A thorough method involves examining running processes and network connections.

• Quick checks: Use netstat -an | findstr ":8080" (Windows) or ss -tulnp | grep :8080 (Linux) to check for the service listening on port 8080.
• Scanning: Nessus plugin ID 16395 can detect Anon Proxy Server. This is an example only.
• Logs and evidence: Check system logs for entries related to the ‘anonproxyserver’ process or connections on proxy ports (e.g., Event Viewer on Windows, /var/log/syslog on Linux).

netstat -an | findstr ":8080"

4. Solution / Remediation Steps

To fix the issue, ensure appropriate security controls are in place for the Anon Proxy Server service. Limit incoming traffic if desired.

4.1 Preparation

• Services: No services need to be stopped unless reconfiguring or removing the software.
• Roll back plan: Restore from the system snapshot if issues occur.

4.2 Implementation

1. Step 1: Review your corporate security policy regarding proxy server usage.
2. Step 2: If the service is not required, uninstall Anon Proxy Server software.
3. Step 3: If the service is required, limit incoming traffic to authorized IP addresses using firewall rules.

4.3 Config or Code Example

Before

# No firewall rule restricting access to port 8080

After

# Firewall rule allowing only specific IP addresses to connect to port 8080 (example using iptables)
iptables -A INPUT -p tcp --dport 8080 -s  -j ACCEPT
iptables -A INPUT -p tcp --dport 8080 -j DROP

4.4 Security Practices Relevant to This Vulnerability

List only practices that directly address this vulnerability type. Use neutral wording and examples instead of fixed advice. For example: least privilege, input validation, safe defaults, secure headers, patch cadence. If a practice does not apply, do not include it.

• Practice 1: Least privilege – restrict access to the proxy server to only authorized users or systems.
• Practice 2: Network segmentation – isolate the proxy server on a separate network segment if possible.

4.5 Automation (Optional)

# Example PowerShell script to block port 8080 with Windows Firewall
New-NetFirewallRule -DisplayName "Block Anon Proxy Server Port" -Direction Inbound -Protocol TCP -LocalPort 8080 -Action Block

5. Verification / Validation

Confirm the fix worked by checking if unauthorized access to the proxy server is blocked. Re-run earlier detection methods and perform a simple service smoke test.

• Post-fix check: Use netstat -an | findstr ":8080" (Windows) or ss -tulnp | grep :8080 (Linux) to confirm the service is still running, but access is restricted.
• Re-test: Re-run the earlier detection methods to show that unauthorized connections are blocked.
• Smoke test: If the proxy server is required, verify authorized users can still connect and use its functionality.
• Monitoring: Monitor system logs for failed connection attempts on port 8080.

netstat -an | findstr ":8080"

6. Preventive Measures and Monitoring

Suggest only measures that are relevant to the vulnerability type. Use “for example” to keep advice conditional, not prescriptive.

• Baselines: Update security baselines or policies to include restrictions on proxy server usage (for example, a CIS control related to network services).
• Pipelines: Add checks in CI/CD pipelines to scan for unauthorized software installations.
• Asset and patch process: Implement a regular asset inventory process to identify and manage all running software.

7. Risks, Side Effects, and Roll Back

• Risk or side effect 1: Blocking port 8080 may disrupt legitimate proxy traffic if not configured correctly.
• Risk or side effect 2: Uninstalling the software could impact applications that rely on it.

8. References and Resources

• Vendor advisory or bulletin: http://anonproxyserver.sourceforge.net/