Skip to content
yararules.org
Menu

YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_EXPL_LOG_CVE_2021_26858_Exchange_Forensic_Artefacts_Mar21_1

Detects forensic artefacts found in HAFNIUM intrusions exploiting CVE-2021-26858

ExploitSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
Florian Roth (Nextron Systems)
Date
2021-03-02
Modified
2021-03-04
Score / Quality
65 / 85

What this rule detects

Detects forensic artefacts found in HAFNIUM intrusions exploiting CVE-2021-26858

It defines 1 patterns (0 text, 0 hex, 1 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
expl-log-cve-2021-26858-exchange-forensic-artefacts-mar21-1.yarDetection Rule License 1.1
rule SIGNATURE_BASE_EXPL_LOG_CVE_2021_26858_Exchange_Forensic_Artefacts_Mar21_1 : LOG CVE_2021_26858
{
	meta:
		description = "Detects forensic artefacts found in HAFNIUM intrusions exploiting CVE-2021-26858"
		author = "Florian Roth (Nextron Systems)"
		id = "f6fa90c7-c2c0-56db-bf7b-dc146761a995"
		date = "2021-03-02"
		modified = "2021-03-04"
		reference = "https://www.volexity.com/blog/2021/03/02/active-exploitation-of-microsoft-exchange-zero-day-vulnerabilities/"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/apt_hafnium_log_sigs.yar#L15-L28"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		logic_hash = "0a8296b7e990e52330412288e9ff71e08a5258fc63c4754e6d0e6d64302f55e6"
		score = 65
		quality = 85
		tags = "LOG, CVE-2021-26858"

	strings:
		$xr1 = /POST (\/owa\/auth\/Current\/themes\/resources\/logon\.css|\/owa\/auth\/Current\/themes\/resources\/owafont_ja\.css|\/owa\/auth\/Current\/themes\/resources\/lgnbotl\.gif|\/owa\/auth\/Current\/themes\/resources\/owafont_ko\.css|\/owa\/auth\/Current\/themes\/resources\/SegoeUI-SemiBold\.eot|\/owa\/auth\/Current\/themes\/resources\/SegoeUI-SemiLight\.ttf|\/owa\/auth\/Current\/themes\/resources\/lgnbotl\.gif)/

	condition:
		$xr1
}

Strings (1 patterns)

IdentifierTypeValueModifiers
$xr1regex/POST (\/owa\/auth\/Current\/themes\/resources\/logon\.css|\/owa\/auth\/Current\/themes\/resources\/owafont_ja\.css|\/owa\/auth\/Current\/themes\/resources\/lgn …

Condition

$xr1

In plain words (Heuristic)

  • Pattern $xr1 must be present.

Test this rule in your browser

Drop a file to scan it with this rule using YARA-X compiled to WebAssembly. Nothing is uploaded.

Drop a file here or click to chooseScanned locally with YARA-X. Files up to 200 MB.

Open in editor

References

Licence & attribution

Author: Florian Roth (Nextron Systems)

Source repository: Signature Base (Florian Roth / Nextron) @ 94a1c48d7a

Licence: Detection Rule License 1.1 (repository licence)

Original rule

Mirrored via YARA Forge 20260927, which prefixes rule names with the source and adds normalised meta fields.

Rule id: f6fa90c7-c2c0-56db-bf7b-dc146761a995

Tags:LOGCVE_2021_26858

Related rules