How to Detect AI Attack Agents and Prevent CDN/WAF Bypass
Summary
Abstract Security shares detection and defense guidance for AI-agent attacks, including identifying CDN/WAF origin bypass, suspicious JA3-to-User-Agent patterns, and anti-forensics activity, with recommendations for firewalling, audits, and off-host logging.
Key points
- The article describes origin-discovery methods that may expose backend IPs, including historical DNS, staging subdomains, certificate data, leaked headers, and favicon searches.
- It recommends restricting origin ports 80/443 to published CDN address ranges and periodically auditing DNS records, subdomains, ports, and favicon exposure.
- AI agents using curl or Python libraries may present multiple forged User-Agent strings over the same TLS fingerprint; the article suggests tuning alerts for this pattern.
- Examples of anti-forensics include timestomping, deleting tools, and altering or clearing logs, sometimes under web-server processes.
- The article recommends monitoring suspicious process activity and file changes, forwarding logs off-host, and reviewing webroot files for recent ctime but older mtime.
- It lists managed detections for Linux and Windows file deletion, timestomping, and log manipulation.
Article Details
- Defense Focus
- Detect and prevent AI-agent attacks that bypass CDN/WAF origin controls, forge User-Agent strings over repeated TLS client libraries, and perform anti-forensics on compromised web servers.
- Detection Methods
- Alert on multiple User-Agent values associated with the same source IP address and JA3 fingerprint; tune thresholds to the environment.
- Correlate WAF, load-balancer, reverse-proxy, and other middleware or security-appliance logs in real time.
- Audit externally visible origin exposure using DNS records, historical DNS, staging-subdomain checks, backend headers, port scans, and favicon-hash searches.
- Monitor web-server process trees for file timestamp changes, shredding or deletion, log tampering, and security-log clearing.
- Hunt for webroot scripts with ctime newer than mtime, recent ctime, old mtime, and no matching deployment; raw inode edits may also be auditable.
- Use file-integrity monitoring to alert on new files in production webroots, including cache and compile-artifact directories.
- Data Sources
- HTTP(S) session logs with source IP, User-Agent, and JA3
- WAF, load-balancer, reverse-proxy, and middleware logs
- DNS A, AAAA, and TXT records; historical DNS data
- Certificate serials, SANs, and certificate-transparency logs
- HTTP response headers and favicon hashes
- Process-creation and parent-child process telemetry on Linux and Windows
- File-integrity events and webroot file ctime/mtime metadata
- Locally collected authentication, syslog, wtmp, systemd journal, and Windows Security event logs
- Remote-forwarded, append-only logs retained in a SIEM
- Rule Types
- JA3-to-User-Agent anomaly correlation
- Origin exposure and CDN/WAF bypass checks
- Linux anti-forensics process-creation detections
- Windows anti-forensics and event-log manipulation detections
- Webroot file-integrity and timestomping detections
- Platforms
- Abstract streaming detection engine and action engine
- SIEM
- Linux
- Windows
- macOS
- Defensive Actions
- Restrict origin firewall access on ports 80 and 443 to the CDN's published IP ranges.
- Run quarterly audits for exposed web subdomains, AAAA/SPF leaks, historical-DNS exposure, unproxied ports, favicon matches, and leaky backend headers.
- Constrain web-user execution with non-interactive or restrictive shells and AppArmor or SELinux.
- Forward authentication and system logs off-host to append-only storage.
- Enable file-integrity monitoring and creation alerts across production webroots, including cache and compile-artifact directories.
- Tune anomaly detection to account for legitimate multiple-User-Agent behavior in the environment.
- Treat anti-forensics alerts as potentially time-sensitive because cleanup may occur immediately after an operation.
MITRE ATT&CK
T1070.001 · Clear Windows Event LogsThe article describes clearing the Windows Security event log with wevtutil.T1070.002 · Clear Linux or Mac System LogsThe article describes removing attacker-related lines from auth.log and rewriting wtmp login records with utmpdump.T1070.003 · Clear Command HistoryThe article describes clearing the systemd journal with journalctl --vacuum-time.T1070.004 · File DeletionThe article describes shredding and deleting temporary tools and files, including use of shred and find.T1070.006 · TimestompThe article describes altering file timestamps, including touch-based backdating and raw inode ctime edits with debugfs.T1190 · Exploit Public-Facing ApplicationThe article describes the agent conducting reconnaissance and active exploitation against web-facing systems, including direct requests to an exposed origin.T1505.003 · Web ShellThe article identifies web shells, including newly appearing JSP/ASP files in production webroots, as persistence mechanisms to monitor.
People
Tools
CensysThe skill supports putting in API keys from 8 different security tools, including Shodan, Censys, and VirusTotal:FOFA# [4] Favicon hash for Shodan/FOFA pivotingFUCK-CDNOne playbook in the recently uncovered adversary AI skill library is called FUCK-CDN (https://github.com/0xShe/FUCK-CDN) and is an adapted, token-cost-optimized open-source methodology for enumerating, then bypassingShodanThe skill supports putting in API keys from 8 different security tools, including Shodan, Censys, and VirusTotal:VirusTotalThe skill supports putting in API keys from 8 different security tools, including Shodan, Censys, and VirusTotal: