Reporting False Positives

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Reporting False Positives when Running ASL

If ASL blocks something it shouldn't you can report a False Positive to our support team by simply clicking the "False Positive" button in the GUI. This will open up a case in the support portal, and if you have setup a support portal account your False Positive will be added to your account for review. If you have ASL configured to send alerts to one of the email addresses associated with your account then you will see your False Positives show up in real time in the support portal. If not, then a member of our support team will have to manually associate your reports with your account and this can take some time.

If you can not use the GUI to report a false positive or you are a rules only member (and therefore do not have the ASL GUI), you can report false positives from the command line. For example, if you have an event like this in your /var/log/httpd/audit_log file:

[modsecurity] [client] [domain] [403] [/20091115/20091115-1635/20091115-163542-rM-wwlKl8i4AACHwQ70AAAAa] [file "/etc/httpd/modsecurity.d/10_asl_rules.conf"] [line "224"] [id "340026"] [rev "49"] [msg " WAF Rules: PHP Injection attempt in URI"] [data ""] [severity "CRITICAL"] Access denied with code 403 (phase 2). Match of "beginsWith http://%{SERVER_NAME}/" against "MATCHED_VAR" required.

The fourth variable, highlighted above as [/20091115/20091115-1635/20091115-163542-rM-wwlKl8i4AACHwQ70AAAAa], is the unique token for the event. If you have ASL installed, you can report it with this command:

asl --report-false-positive /20091115/20091115-1635/20091115-163542-rM-wwlKl8i4AACHwQ70AAAAa

Reporting False Positives when not running ASL

If you are running the Atomic ModSecurity Rules and you are not running ASL then you will need to report a false positive manually. modsecurity does not come with a simple tool for reporting false positives as ASL does.

First you must ensure that you have setup modsecurity properly to log events in enough detail that we can help you. If you followed the instructions on the Atomic ModSecurity Rules page you should have audit logging setup correctly and will have a directory called:


This directory will create a special directory for each event that is blocked on your system by first creating a unique directory for today. The format of the directory is YEARMONTHDATE. For example, if an event occurred on November 25th, 2009, there would a directory of the following format:


Within that directory will be subdirectories that correspond to events that happen at specific time. The format is YEARMONTHDAY-HOURMINUTE. So if an event occured at 17:23 hours on November 25th, 2009, the corresponding directory would be:


Inside this directory will be the audit payloads of all the events that occured in that time period. If many events occured within that minute there will be multiple files. The /var/log/http/audit_log file will contain a running log of the events so you can look up the directories they are stored in. For example this audit_log entry:

[modsecurity] [client] [domain] [403] [/20091125/20091125-1723/20091125-172310-gPA9rUrQYacAACJpX@UAAAAK] [file "/etc/httpd/modsecurity.d/10_asl_antimalware.conf"] [line "42"] [id "360000"] [rev "2"] [msg " Malware Blacklist: Malware Site detected in Argument (AE)"] [data ""] [severity "CRITICAL"] Access denied with code 403 (phase 2). Matched phrase "" at ARGS:sourcedir.

The payload for this event can be found by looking at the highlighted line above, and appending /var/asl/data/audit. For example:

 cat    /var/asl/data/audit/20091125/20091125-1723/20091125-172310-gPA9rUrQYacAACJpX@UAAAAK

Would produce the actual payload of the attack. In this case the example attack looks like this:

[25/Nov/2009:17:23:10 --0500] gPA9rUrQYacAACJpX@UAAAAK 55732 80
GET /delayed/rules/modsec/?sourcedir= HTTP/1.1
TE: deflate,gzip;q=0.3
Connection: TE, close
User-Agent: Mozilla/5.0

HTTP/1.1 403 Forbidden
Content-Length: 303
Connection: close
Content-Type: text/html; charset=iso-8859-1

Message:  [file "/etc/httpd/modsecurity.d/10_asl_antimalware.conf"] [line "42"] [id "360000"] [rev "2"] [msg " Malware Blacklist: Malware Site detected in Argument (AE)"] [data ""] [severity "CRITICAL"] Access denied with code 403 (phase 2). Matched phrase "" at ARGS:sourcedir.
Action: Intercepted (phase 2)
Stopwatch: 1259187790167469 27763 (4424 27390 -)
Producer: ModSecurity for Apache/2.5.11 (; 200911221938.
Server: Apache/2.2.3 (CentOS)


To report this as a false positive, you will need to include:

  1. Your account name (if this is for the real time rules)
  2. The version of the rules you are running
  3. The version of mod_security you are running
  4. The platform you are running on (Linux distribution, apache version).
  5. The output of /var/asl/data/audit/20091125/20091125-1723/20091125-172310-gPA9rUrQYacAACJpX@UAAAA (or whatever it is for your system)

Then e-mail this to Our CRM will automatically open a case for you to track the incident. The apache error_log file is of no use to us, so please do not send it. It does not contain any of the information we need to investigate a false positive.

If you are RealTime feed customer, you are encouraged to open a support portal account.

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