Hey everyone, I've been deep-diving into our security stack and a recent report about Magecart-style attacks got me thinking. We use AWS WAF on our e-commerce properties, and I'm trying to figure out if it's a realistic tool to help block credit card skimming JavaScript.
From what I've pieced together, the classic approach seems to be:
* Writing rules to block requests to known malicious domains (like skimmer C2 endpoints).
* Trying to detect obfuscated JS patterns in `` tags or inline handlers.
* Monitoring for anomalous POST requests that might be exfiltrating data.
But the skimmers keep evolving. I'm curious about practical, real-world implementations.
Has anyone here actually built and maintained a WAF ruleset that effectively caught a skimmer? I'm especially interested in:
* Which rule groups (Managed or custom) proved most valuable? The managed `CoreRuleSet` or `KnownBadInputs`?
* Did you use regex in a `ByteMatchStatement` to scan for patterns? How did you avoid false positives on legitimate minified code?
* Was combining WAF with something like Amazon GuardDuty for S3 monitoring necessary?
* Any major pitfalls? I'm worried about performance hits with deep inspection.
I started a basic comparison of managed vs. custom rules for this use case, but it's all theory without real battle stories. If you've run this playbook, I'd love to hear what worked and what was a total time-sink. A link to any sanitized rule examples or a workflow diagram would be amazing.
Yes, but it's a layer, not a solution.
The managed rule groups are useless for catching novel skimmers. They're for known attack patterns. You need custom rules focused on outbound traffic. I built a set using `ByteMatchStatement` and `RegexPatternSetReferenceStatement` to look for patterns in `` src attributes and form action URLs. The trick is to target the exfiltration, not the obfuscated payload.
Performance hit was minimal because the rules only inspect specific parts of the request. The real pitfall is maintenance. You're in an arms race. I had to update regex bi-weekly as skimmer domains changed patterns.
GuardDuty for S3 is for a different stage - that's if they've already compromised your bucket. WAF is for blocking the initial call-out or data exfil. You need both, plus CSP headers.
Benchmarks > marketing.