EvidenceSheet
PCI DSS v4.0.1 · Req 6: Secure Systems and Software

6.4.2 Automated web attack detection and prevention

Public-facing web applications must be protected by an automated technical control that constantly spots and stops web-based attacks and that, at minimum: is placed ahead of the public-facing web applications and configured to find and block web-based attacks; runs actively and is kept updated where relevant; produces audit logs; and is set either to block web-based attacks or to raise an alert that is investigated immediately. It applies to all entities with public-facing web applications. Applicability: this newer requirement takes the place of 6.4.1 from the date it became effective. Objective under the customized approach: public-facing web applications are defended against malicious attacks in real time. Future-dated: treated as a best practice up to 31 March 2025 and mandatory since then.

Source: PCI DSS v4.0.1, 6.4.2. The statement above is our statement of the clause, read from the published text and cited so you can check it against the official text, not the instrument verbatim. Open PCI DSS v4.0.1 in the compliance library.

Version 4.0.1 is the active version; 4.0 has been retired. Appendix A1 applies only to multi-tenant service providers, A2 only to card-present POS POI terminals that still use SSL or early TLS, and A3 only when a payment brand or acquirer requires it. Which requirements apply to you follows your validation type.

5
artefacts
3
held by a system
1
at each review
easy
to go live
SIEM / log platform
where the evidence lives
teal = a system already holds it · olive = produced at each review. To go live: easy when half or more of the artefacts are already held by a system, moderate from a quarter to a half, hard below a quarter.

These are the artefacts auditors commonly ask for on this requirement, our guidance rather than text from the standard. Your assessor decides what is sufficient in your context, and asks for samples across the period when a report covers one.

system holds itEvidence a system already holds

  • WAF configuration export showing blocking mode or alerting settings · SIEM / log platform
  • WAF audit logs forwarded to the log management system · SIEM / log platform
  • Alert investigation tickets with response timestamps · SIEM / log platform

periodic reviewEvidence produced at each review

  • Rule set and signature update records · Document repository

governing documentDocuments that govern the control

  • Network or architecture diagram showing the WAF or equivalent in front of every public web application · Policy repository / GRC workspace

First move

Automate the pull from your SIEM / log platform. Retention and alert rules exported from the SIEM; review evidence is the closed-alert record with reviewer and time.

Common gaps auditors find

Do this for your whole sheet

Paste the rows you run your controls from and get this mapping for every control at once, with the periodic-review ones flagged and a first move per row. No account for the first run.

Build my evidence sheet

6.4.1 Public web application review or automated protection · 6.4.3 Payment page script management