Small Sieve Malware File Indicator Creation

 1title: Small Sieve Malware File Indicator Creation
 2id: 39466c42-c189-476a-989f-8cdb135c163a
 3status: test
 4description: Detects filename indicators that contain a specific typo seen used by the Small Sieve malware.
 5references:
 6    - https://www.ncsc.gov.uk/static-assets/documents/malware-analysis-reports/small-sieve/NCSC-MAR-Small-Sieve.pdf
 7author: Nasreddine Bencherchali (Nextron Systems), X__Junior (Nextron Systems)
 8date: 2023/05/19
 9tags:
10    - attack.defense_evasion
11    - attack.t1036.005
12    - detection.emerging_threats
13logsource:
14    product: windows
15    category: file_event
16detection:
17    selection_typo_path:
18        TargetFilename|contains|all:
19            - ':\Users\'
20            - '\AppData\'
21        TargetFilename|contains:
22            - '\Roaming\'
23            - '\Local\'
24    selection_typo_keyword:
25        TargetFilename|contains: 'Microsift'
26    selection_ioc:
27        TargetFilename|endswith: '\AppData\Local\MicrosoftWindowsOutlookDataPlus.txt'
28    condition: all of selection_typo_* or selection_ioc
29falsepositives:
30    - Unlikely
31level: high