XSS Attempt
Attack scenariohttp:exploitMITRE T1595.002
- Version
- 0.4
- Name
- crowdsecurity/http-xss-probing
- Remediation
- Ban
A scenario that detects XSS probing with minimal false positives
Install with a top-level collection
16 collections include itsudo cscli collections install crowdsecurity/aws-cloudfrontInstalls 2 parsers and 47 scenarios, via HTTP - Generic Protection.
View AWS CloudFront →Installation
sudo cscli scenarios install crowdsecurity/http-xss-probingThen reload CrowdSec: sudo systemctl reload crowdsec
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type: leaky#requires at least 2.0 because it's using the 'data' section and the 'Upper' expr helperformat: 2.0name: crowdsecurity/http-xss-probbingdata:- source_url: https://hub-data.crowdsec.net/web/xss_probe_patterns.txtdest_file: xss_probe_patterns.txttype: stringdescription: "A scenario that detects XSS probing with minimal false positives"filter: "evt.Meta.log_type in ['http_access-log', 'http_error-log'] && any(File('xss_probe_patterns.txt'), {Upper(evt.Parsed.http_args) contains Upper(#)})"groupby: evt.Meta.source_ipcapacity: 5leakspeed: 1sblackhole: 5m#low false positives approach : we require distinct payloads to avoid false positivesdistinct: evt.Parsed.http_argslabels:remediation: trueclassification:- attack.T1595.002behavior: "http:exploit"label: "XSS Attempt"spoofable: 0service: httpconfidence: 3
Installed on
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Documentation
The http XSS probing scenario aims at detecting, with very little false positive chances, XSS probing attempts.
XSS probing attempts will be characterized by the presence of specific XSS related patterns in uri/GET arguments (if and when this is where the injected parameter is), and this is what this scenario detects.
The word list is picked specifically to limit false positives.
Furthermore, a distinct directive is present on the get parameters themselves to reduce false positive chances.
WARNING This scenario is not a WAF, and this scenario does not aims at replacing a WAF. A motivated attacker with knowledge of crowdsec will be able to bypass it. It is mostly meant to be a way to detect generic XSS probing.