Network Connection via Registration Utility

edit

Identifies the native Windows tools regsvr32.exe, regsvr64.exe, RegSvcs.exe, or RegAsm.exe making a network connection. This may be indicative of an attacker bypassing allowlists or running arbitrary scripts via a signed Microsoft binary.

Rule type: eql

Rule indices:

  • winlogbeat-*
  • logs-endpoint.events.*

Severity: low

Risk score: 21

Runs every: 5 minutes

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

Tags:

  • Elastic
  • Host
  • Windows
  • Threat Detection
  • Execution

Version: 6 (version history)

Added (Elastic Stack release): 7.6.0

Last modified (Elastic Stack release): 7.11.0

Rule authors: Elastic

Rule license: Elastic License

Potential false positives

edit

Security testing may produce events like this. Activity of this kind performed by non-engineers and ordinary users is unusual.

Rule query

edit
sequence by process.entity_id [process where (process.name :
"regsvr32.exe" or process.name : "regsvr64.exe" or
process.name : "RegAsm.exe" or process.name : "RegSvcs.exe") and
event.type == "start"] [network where (process.name : "regsvr32.exe"
or process.name : "regsvr64.exe" or process.name :
"RegAsm.exe" or process.name : "RegSvcs.exe") and not
cidrmatch(destination.ip, "10.0.0.0/8", "169.254.169.254",
"172.16.0.0/12", "192.168.0.0/16")]

Threat mapping

edit

Framework: MITRE ATT&CKTM

Rule version history

edit
Version 6 (7.11.0 release)
  • Formatting only
Version 5 (7.10.0 release)
  • Rule name changed from: Network Connection via Regsvr
  • Updated query, changed from:

    event.category:network and event.type:connection and
    process.name:(regsvr32.exe or regsvr64.exe) and not
    destination.ip:(10.0.0.0/8 or 169.254.169.254 or 172.16.0.0/12 or
    192.168.0.0/16)
Version 4 (7.9.1 release)
  • Formatting only
Version 3 (7.9.0 release)
  • Updated query, changed from:

    process.name:(regsvr32.exe or regsvr64.exe) and event.action:"Network
    connection detected (rule: NetworkConnect)" and not
    destination.ip:(10.0.0.0/8 or 169.254.169.254 or 172.16.0.0/12 or
    192.168.0.0/16)
Version 2 (7.7.0 release)
  • Updated query, changed from:

    (process.name:regsvr32.exe or process.name:regsvr64.exe) and
    event.action:"Network connection detected (rule: NetworkConnect)" and
    not destination.ip:169.254.169.254/32 and not
    destination.ip:10.0.0.0/8 and not destination.ip:172.16.0.0/12 and not
    destination.ip:192.168.0.0/16