Search-ms and WebDAV Indicators in URL

 1title: Search-ms and WebDAV Indicators in URL
 2id: 5039f3d2-406a-4c1a-9350-7a5a85dc84c2
 3status: experimental
 4description: Detects URL pattern used by search(-ms)/WebDAV initial access campaign.
 5references:
 6    - https://www.trellix.com/en-us/about/newsroom/stories/research/beyond-file-search-a-novel-method.html
 7author: Micah Babinski
 8date: 2023/07/31
 9modified: 2023/08/04
10tags:
11    - attack.initial_access
12    - attack.t1584
13    - attack.t1566
14logsource:
15    category: proxy
16detection:
17    selection_search_ms:
18        c-uri|contains|all:
19            - 'search' # matches on search:query= or search-ms:query=
20            - ':query='
21            - 'webdav'
22    selection_search_term:
23        c-uri|contains:
24            - 'invoice'
25            - 'payment'
26            - 'notice'
27            - 'agreement'
28            # add others!
29    filter:
30        dst_ip:
31            - '127.0.0.0/8'
32            - '10.0.0.0/8'
33            - '172.16.0.0/12'
34            - '192.168.0.0/16'
35    condition: all of selection_* and not filter
36falsepositives:
37    - Legitimate use of search-ms/search URI protocol
38level: high```