Suspicious DNS Queries Containing Base64-Padding Pattern (==.)

Alerts on DNS queries containing the base64 delimiter pattern '==.' consistent with encoded data in DNS.

FreeReviewedSigma · Medium · v2

Category: dns
Author: Florian Roth (Nextron Systems) (SigmaHQ), DRL 1.1
Published: 2018-05-10
Updated: 2026-07-31

ATT&CK techniques

C2 → Exfiltration

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
- T1071.004DNS
Exfiltration
- T1048.003Exfiltration Over Unencrypted Non-C2 Protocol
Impact

What it detects

This rule flags DNS queries whose query name contains the base64 padding pattern "==.". Attackers may embed encoded data in DNS query strings to obscure content during exfiltration or command-and-control. The detection relies on DNS query text telemetry and matches the specific substring indicator within the query field.

Reporting behind it

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Suspicious DNS Queries Containing Base64-Padding Pattern (==.)

Pivot detection · T1071.004 · 9 related

Changelog

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

suspicious-dns-queries-containing-base64-delimiters-4153a907

title: Suspicious DNS Queries Containing Base64-Padding Pattern (==.)
id: 52382811-fb74-4092-8312-e48ad04971ed
status: test
description: This rule flags DNS queries whose query name contains the base64 padding pattern "==.". Attackers may embed encoded data in DNS query strings to obscure content during exfiltration or command-and-control. The detection relies on DNS query text telemetry and matches the specific substring indicator within the query field.
references:
  - https://github.com/krmaxwell/dns-exfiltration
  - https://github.com/SigmaHQ/sigma/blob/master/rules/network/dns/net_dns_susp_b64_queries.yml
author: Florian Roth (Nextron Systems), Huntrule Team
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
license: DRL-1.1
related:
  - id: 4153a907-2451-4e4f-a578-c52bb6881432
    type: derived

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