Detection rules › Sigma

Network login performed to multiple targets

Status
experimental
Severity
high
Time window
15m
Log source
product windows, service security
Author
mdecrevoisier
Source
github.com/mdecrevoisier/SIGMA-detection-rules

Detects scenarios where an attacker would attempt to enumerate hosts resources and execute a payload with a compromised account. Vulnerability scanners, enumeration software or tool like SharepHound/CrackMapexec may generate such behavior.

MITRE ATT&CK coverage

TacticTechniques
Initial AccessT1078 Valid Accounts
DiscoveryT1046 Network Service Discovery

Event coverage

Rule body yaml

title: Network login performed to multiple targets
description: Detects scenarios where an attacker would attempt to enumerate hosts resources and execute a payload with a compromised account. Vulnerability scanners, enumeration software or tool like SharepHound/CrackMapexec may generate such behavior.
references:
- https://medium.com/@Shorty420/enumerating-ad-98e0821c4c78
- https://book.hacktricks.xyz/pentesting/pentesting-smb
- https://0xdf.gitlab.io/2018/12/02/pwk-notes-smb-enumeration-checklist-update1.html
tags:
- attack.discovery
- attack.t1046 # network service scanning
- attack.initial_access
- attack.t1078 # valid accounts
author: mdecrevoisier
status: experimental
logsource:
  product: windows
  service: security
detection:
  selection:
    EventID: 4624
    TargetUserSid|startswith: S-1-5-21-
    LogonType: 3
  filter:
    IpAddress:
      - '%vulnerability_scanners%'
      - '%admin_jump_hosts%'
      - '127.0.0.1'
      - '::1'
  condition: selection and not filter | count(Computer) by IpAddress > 20 # Count of many computer are reporting connection attemps from a single source IP
  timeframe: 15m
falsepositives:
- VAS scanners, administrator jump host, backup solutions, monitoring solutions
level: high

Stages and Predicates

Stage 0: condition

selection and not filter | count(Computer) by IpAddress > 20 # Count of many computer are reporting connection attemps from a single source IP

Stage 1: selection

selection:
  EventID: 4624
  TargetUserSid|startswith: S-1-5-21-
  LogonType: 3
Threshold
> 20

Stage 2: not filter

filter:
  IpAddress:
    - '%vulnerability_scanners%'
    - '%admin_jump_hosts%'
    - '127.0.0.1'
    - '::1'

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

FieldKindExcluded values
IpAddresseq%admin_jump_hosts%
IpAddresseq%vulnerability_scanners%
IpAddresseq127.0.0.1
IpAddresseq::1

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
LogonTypeeq
  • 3 corpus 40 (splunk 13, sigma 12, elastic 9, kusto 6)
TargetUserSidstarts_with
  • S-1-5-21- corpus 3 (sigma 3)