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Detection rules › Sigma

Suspicious DNS Query with B64 Encoded String

Status
test
Severity
medium
Log source
category dns
Author
Florian Roth (Nextron Systems)
Source
github.com/SigmaHQ/sigma

Detects suspicious DNS queries using base64 encoding

MITRE ATT&CK coverage

TacticTechniques
Command & ControlT1071.004 Application Layer Protocol: DNS
ExfiltrationT1048.003 Exfiltration Over Alternative Protocol: Exfiltration Over Unencrypted Non-C2 Protocol

Rule body yaml

title: Suspicious DNS Query with B64 Encoded String
id: 4153a907-2451-4e4f-a578-c52bb6881432
status: test
description: Detects suspicious DNS queries using base64 encoding
references:
    - https://github.com/krmaxwell/dns-exfiltration
author: Florian Roth (Nextron Systems)
date: 2018-05-10
modified: 2022-10-09
tags:
    - attack.exfiltration
    - attack.t1048.003
    - attack.command-and-control
    - attack.t1071.004
logsource:
    category: dns
detection:
    selection:
        query|contains: '==.'
    condition: selection
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    query|contains: '==.'

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
querymatch
  • ==.