Latest SamSA ransomware samples

Hunt Hypothesis

This detection rule identifies recent SamSA ransomware activity by monitoring for specific file execution patterns and encryption behaviors associated with the latest malware variants. Proactively hunting for these indicators in Azure Sentinel is critical to establish early visibility into potential lateral movement and data exfiltration before a full-scale encryption event occurs, even at low severity levels.

YARA Rule

rule SamSam_Ransomware_Latest
{
   meta:
      description = "Latest SamSA ransomware samples"
      author = "Christiaan Beek"
      reference = "http://blog.talosintelligence.com/2018/01/samsam-evolution-continues-netting-over.html"
      date = "2018-01-23"
      hash1 = "e7bebd1b1419f42293732c70095f35c8310fa3afee55f1df68d4fe6bbee5397e"
      hash2 = "72832db9b951663b8f322778440b8720ea95cde0349a1d26477edd95b3915479"
      hash3 = "3531bb1077c64840b9c95c45d382448abffa4f386ad88e125c96a38166832252"
      hash4 = "88d24b497cfeb47ec6719752f2af00c802c38e7d4b5d526311d552c6d5f4ad34"
      hash5 = "8eabfa74d88e439cfca9ccabd0ee34422892d8e58331a63bea94a7c4140cf7ab"
      hash6 = "88e344977bf6451e15fe202d65471a5f75d22370050fe6ba4dfa2c2d0fae7828"

   strings:
      $s1 = "bedf08175d319a2f879fe720032d11e5" fullword wide
      $s2 = "ksdghksdghkddgdfgdfgfd" fullword ascii
      $s3 = "osieyrgvbsgnhkflkstesadfakdhaksjfgyjqqwgjrwgehjgfdjgdffg" fullword ascii
      $s4 = "5c2d376c976669efaf9cb107f5a83d0c" fullword wide
      $s5 = "B917754BCFE717EB4F7CE04A5B11A6351EEC5015" fullword ascii
      $s6 = "f99e47c1d4ccb2b103f5f730f8eb598a" fullword wide
      $s7 = "d2db284217a6e5596913e2e1a5b2672f" fullword wide
      $s8 = "0bddb8acd38f6da118f47243af48d8af" fullword wide
      $s9 = "f73623dcb4f62b0e5b9b4d83e1ee4323" fullword wide
      $s10 = "916ab48e32e904b8e1b87b7e3ced6d55" fullword wide
      $s11 = "c6e61622dc51e17195e4df6e359218a2" fullword wide
      $s12 = "2a9e8d549af13031f6bf7807242ce27f" fullword wide
      $s13 = "e3208957ad76d2f2e249276410744b29" fullword wide
      $s14 = "b4d28bbd65da97431f494dd7741bee70" fullword wide
      $s15 = "81ee346489c272f456f2b17d96365c34" fullword wide
      $s16 = "94682debc6f156b7e90e0d6dc772734d" fullword wide
      $s17 = "6943e17a989f11af750ea0441a713b89" fullword wide
      $s18 = "b1c7e24b315ff9c73a9a89afac5286be" fullword wide
      $s19 = "90928fd1250435589cc0150849bc0cff" fullword wide
      $s20 = "67da807268764a7badc4904df351932e" fullword wide

      $op0 = { 30 01 00 2b 68 79 33 38 68 34 77 65 36 34 74 72 }
      $op1 = { 01 00 b2 04 00 00 01 00 84 }
      $op2 = { 68 09 00 00 38 66 00 00 23 55 53 00 a0 6f 00 00 }

   condition:
      ( uint16(0) == 0x5a4d and
        filesize < 100KB and
        pe.imphash() == "f34d5f2d4577ed6d9ceec516c1f5a744" and ( 8 of them ) and all of ($op*)
      ) or ( all of them )
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

Microsoft Defender for Endpoint — Custom indicators / advanced hunting
Email Gateway — Attachment scanning
File Share Monitoring — Periodic scanning of shared drives
YARA CLI — Manual threat hunting on endpoints

This rule contains 23 string patterns in its detection logic.

References

False Positive Guidance

Here are 5 specific false positive scenarios for the Latest SamSA ransomware samples detection rule, including suggested filters and exclusions tailored for an enterprise environment:

Scheduled Antivirus Definition Updates
- Scenario: The endpoint protection agent (e.g., CrowdStrike Falcon, SentinelOne, or Microsoft Defender) automatically downloads and stages the latest virus definition packs. These updates often contain new heuristic signatures that match the “Latest SamSA” behavioral patterns before they are fully integrated, triggering a scan alert on the update service itself.
- Filter/Exclusion: Exclude processes running under the specific antivirus vendor’s service account (e.g., NT SERVICE\DefenderSvc or LocalSystem) where the parent process is the update orchestrator (e.g., mpcmdrun.exe or falcon.sys). Additionally, whitelist file paths within the vendor’s installation directory (e.g., C:\Program Files\CrowdStrike\*).
Enterprise Backup and Snapshot Operations
- Scenario: Automated backup agents (such as Veeam Backup & Replication, Commvault, or Rubrik) perform incremental backups of critical file servers. During the “pre-scan” phase, these agents read large volumes of files rapidly to calculate checksums, mimicking the rapid file enumeration and modification behavior characteristic of SamSA ransomware reconnaissance.
- Filter/Exclusion: Create a rule exclusion for processes named VeeamAgent.exe, SimAgent.exe, or rubrik-agent running during scheduled maintenance windows (e.g., 02:00–06:00 local time). Filter alerts where the source IP belongs to the dedicated backup subnet and the destination files are located in known backup staging directories.
Patch Management Deployment Tasks
- Scenario: Configuration management tools like **Microsoft