Bug ID 680244: Unable to force Bot Defense action to captcha_challenge in iRule for Suspicious Browsers

Last Modified: Apr 19, 2021

Bug Tracker

Affected Product:  See more info
BIG-IP ASM(all modules)

Known Affected Versions:
12.1.0, 12.1.0 HF1, 12.1.0 HF2, 12.1.1, 12.1.1 HF1, 12.1.1 HF2, 12.1.2, 12.1.2 HF1, 12.1.2 HF2, 12.1.3, 12.1.3.1, 12.1.3.2, 12.1.3.3, 12.1.3.4, 12.1.3.5, 12.1.3.6, 12.1.3.7, 12.1.4, 12.1.4.1, 12.1.5, 12.1.5.1, 12.1.5.2, 12.1.5.3, 12.1.6, 13.0.0, 13.0.0 HF1, 13.0.0 HF2, 13.0.0 HF3, 13.0.1

Fixed In:
13.1.0

Opened: Aug 25, 2017
Severity: 3-Major
Related AskF5 Article:
K25415554

Symptoms

When a request is being blocked (tcp_rst) due to being a suspicious browser, the action cannot be forced to captcha_challenge in the iRule.

Impact

The bot defense action cannot be forced to 'captcha_challenge'. The TCP RST will still be sent.

Conditions

This occurs when a tcp_rst bot defense action is triggered on a suspicious browser, and you want to change the action to captcha_challenge.

Workaround

Change the dosl7.browser_legit_min_score_drop db variable so that all suspicious browsers will be responded with the CAPTCHA challenge instead of getting blocked. To do so, run the following command: tmsh modify sys db dosl7.browser_legit_min_score_drop value 999 Then, you can selectively block requests using the 'BOTDEFENSE::action tcp_rst' command in selected conditions.

Fix Information

It is now possible to use BOTDEFENSE iRules to change the action of a Suspicious Browser from tcp_rst to captcha_challenge.

Behavior Change