Cisco Duo Successful MFA Authentication Via Bypass Code

calendar Apr 17, 2024 · attack.credential_access attack.defense_evasion attack.initial_access  ·
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Detects when a successful MFA authentication occurs due to the use of a bypass code. A bypass code is a temporary passcode created by an administrator for a specific user to access a Duo-protected application. These are generally used as "backup codes," so that enrolled users who are having problems with their mobile devices (e.g., mobile service is disrupted, the device is lost or stolen, etc.) or who temporarily can't use their enrolled devices (on a plane without mobile data services) can still access their Duo-protected systems.

Sigma rule (View on GitHub)

 1title: Cisco Duo Successful MFA Authentication Via Bypass Code
 2id: 6f7e1c10-2dc9-4312-adb6-9574ff09a5c8
 3status: experimental
 4description: |
 5    Detects when a successful MFA authentication occurs due to the use of a bypass code.
 6    A bypass code is a temporary passcode created by an administrator for a specific user to access a Duo-protected application. These are generally used as "backup codes," so that enrolled users who are having problems with their mobile devices (e.g., mobile service is disrupted, the device is lost or stolen, etc.) or who temporarily can't use their enrolled devices (on a plane without mobile data services) can still access their Duo-protected systems.    
 7references:
 8    - https://duo.com/docs/adminapi#logs
 9    - https://help.duo.com/s/article/6327?language=en_US
10author: Nikita Khalimonenkov
11date: 2024/04/17
12tags:
13    - attack.credential_access
14    - attack.defense_evasion
15    - attack.initial_access
16logsource:
17    product: cisco
18    service: duo
19detection:
20    selection:
21        event_type: authentication
22        reason: bypass_user
23    condition: selection
24falsepositives:
25    - Legitimate user that was assigned on purpose to a bypass group
26level: medium

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