Sigma rule: Malware User Agent

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-c0d345fe9065, updated 2024-04-14T00:00:00.000Z.

Rule

Title: Malware User Agent
Status: test
Level: high
Author: Florian Roth (Nextron Systems), X__Junior (Nextron Systems), Nasreddine Bencherchali (Nextron Systems)
Date: 2017-07-08
Modified: 2024-04-14
File: rules/web/proxy_generic/proxy_ua_malware.yml
Commit: ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects suspicious user agent strings used by malware in proxy logs

Log source

category: proxy

Detection

selection:
    c-useragent:
        # RATs
        - 'Mozilla/5.0 (Windows NT 6.1; WOW64; rv:53.0) Gecko/20100101 Chrome /53.0' # DragonOK
        - 'Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1)' # Used by PlugX - base-lining recommended - https://community.rsa.com/thread/185439
        - 'Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0)' # Used by PlugX - base-lining recommended - https://community.rsa.com/thread/185439
        - 'Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0; .NET CLR  1.1.4322)' # Used by PlugX - old - https://unit42.paloaltonetworks.com/unit-42-identifies-new-dragonok-backdoor-malware-deployed-against-japanese-targets/
        - 'HttpBrowser/1.0' # HTTPBrowser RAT
        - '*<|>*' # Houdini / Iniduoh / njRAT
        - 'nsis_inetc (mozilla)' # ZeroAccess
        - 'Wget/1.9+cvs-stable (Red Hat modified)' # Dyre / Upatre
        # Ghost419 https://www.mcafee.com/blogs/other-blogs/mcafee-labs/gold-dragon-widens-olympics-malware-attacks-gains-permanent-presence-on-victims-systems/
        - 'Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; Trident/4.0; .NET CLR 1.1.4322)'
        # Malware
        - '*zeroup*' # W32/Renos.Downloader
        - 'Mozilla/5.0 (Windows NT 5.1 ; v.*' # Kazy
        - '* adlib/*'
        - '* tiny' # Trojan Downloader
        - '* BGroom *' # Trojan Downloader
        - '* changhuatong'
        - '* CholTBAgent'
        - 'Mozilla/5.0 WinInet'
        - 'RookIE/1.0'
        - 'M' # HkMain
        - 'Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0)' # Egamipload - old UA - probable prone to false positives
        - 'Mozilla/4.0 (compatible;MSIE 7.0;Windows NT 6.0)' # Yakes
        - 'backdoorbot'
        - 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.1 (.NET CLR 3.5.30731)' # Sality
        - 'Opera/8.81 (Windows NT 6.0; U; en)' # Sality
        - 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.1 (.NET CLR 3.5.30729)' # Sality
        - 'Opera' # Trojan Keragany
        - 'Mozilla/4.0 (compatible; MSIE 5.0; Windows 98)' # Fareit
        - 'Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)' # Webshell's back connect
        - 'MSIE' # Toby web shell
        - '*(Charon; Inferno)' # Loki Bot
        - 'Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/5.0)' # Fareit / Pony
        - 'Mozilla/4.0 (compatible; MSIE 6.1; Windows NT)' # https://www.virustotal.com/gui/file/8abbef8e58f012d45a7cb46c3c2729dcd33cf53e721ff8c59e238862aa0a9e0e/detection
        - 'Mozilla/4.0(compatible; MSIE 6.0; Windows NT 5.1)' # MacControl malware https://www.virustotal.com/gui/file/d60f61f1f03a5011a0240694e110c6d370bf68a92753093186c6d14e26a15428/detection https://www.symantec.com/connect/blogs/osxmacontrol-back-it-again
        - 'Mozilla/5.0 (Windows NT 10.0; Win64; x64)' # used by Zebrocy malware https://app.any.run/tasks/7d7fa4a0-6970-4428-828b-29572abf9ceb/
        # Ursnif
        - 'Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 10.0; Win64; x64)'
        - 'Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; Win64; x64)'
        # Emotet
        - 'Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.2; WOW64; Trident/7.0; .NET4.0C; .NET4.0E; InfoPath.3)' # https://twitter.com/webbthewombat/status/1225827092132179968
        # Lockbit (https://twitter.com/kladblokje_88/status/1614673320124743681?s=12&t=joEpeVa5d58aHYNGA_To7Q)
        - 'Mozilla/5.0 (Windows NT 6.1)'
        - 'AppleWebkit/587.38 (KHTML, like Gecko)'
        - 'Chrome/91.0.4472.77'
        - 'Safari/537.36'
        - 'Edge/91.0.864.37'
        - 'Firefox/89.0'
        - 'Gecko/20100101'
        # Others
        - '* pxyscand*'
        - '* asd'
        - '* mdms'
        - 'sample'
        - 'nocase'
        - 'Moxilla'
        - 'Win32 *'
        - '*Microsoft Internet Explorer*'
        - 'agent *'
        - 'AutoIt' # Suspicious - base-lining recommended
        - 'IczelionDownLoad'
        - 'Mozilla/4.0 (compatible; MSIE 9.0; Windows NT 10.0; .NET4.0C; .NET4.0E; Tablet PC 2.0)' # https://unit42.paloaltonetworks.com/thor-plugx-variant/
        - 'record' # https://blog.sekoia.io/raccoon-stealer-v2-part-1-the-return-of-the-dead/
        - 'mozzzzzzzzzzz' # https://blog.sekoia.io/raccoon-stealer-v2-part-1-the-return-of-the-dead/
        - 'Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:76.0) Gecko/20100101 Firefox/76.0' # Quasar RAT UA https://twitter.com/malmoeb/status/1559994820692672519?s=20&t=g3tkNL09dZZWbFN10qDVjg
        - 'Havana/0.1' # https://www.cybereason.com/blog/threat-alert-havanacrypt-ransomware-masquerading-as-google-update
        - 'antSword/v2.1' # AntSword Webshell UA
        - 'rqwrwqrqwrqw'  # Racoon Stealer
        - 'qwrqrwrqwrqwr'  # Racoon Stealer
        - 'rc2.0/client'  # Racoon Stealer
        - 'TakeMyPainBack'  # Racoon Stealer
        - 'xxx' # Racoon Stealer
        - '20112211' # Racoon Stealer
        - '23591' # Racoon Stealer
        - '901785252112' # Racoon Stealer
        - '1235125521512' # Racoon Stealer
        - '125122112551' # Racoon Stealer
        - 'B1D3N_RIM_MY_ASS' # Racoon Stealer
        - 'AYAYAYAY1337' # Racoon Stealer
        - 'iMightJustPayMySelfForAFeature' # Racoon Stealer
        - 'ForAFeature' # Racoon Stealer
        - 'Ares_ldr_v_*' # AresLoader
        # - 'Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:106.0) Gecko/20100101 Firefox/106' # seen used by AresLoader
        - 'Microsoft Internet Explorer' # https://github.com/silence-is-best/c2db
        - 'CLCTR' # https://github.com/silence-is-best/c2db
        - 'uploader' # https://github.com/silence-is-best/c2db
        - 'agent' # https://github.com/silence-is-best/c2db
        - 'License' # https://github.com/silence-is-best/c2db
        - 'vb wininet' # https://github.com/silence-is-best/c2db
        - 'Client' # https://github.com/silence-is-best/c2db
        - 'Lilith-Bot/3.0' # Lilith Stealer - https://twitter.com/suyog41/status/1558051450797690880
        - 'svc/1.0' # SVC Loader - https://twitter.com/suyog41/status/1558051450797690880
        - 'WSHRAT' # WSHRAT - https://twitter.com/suyog41/status/1558051450797690880
        - 'ZeroStresser Botnet/1.5' # Zerobot - https://twitter.com/suyog41/status/1558051450797690880
        - 'OK' # Nymaim - https://twitter.com/suyog41/status/1558051450797690880
        - 'Project1sqlite' # DarkCloud - https://twitter.com/suyog41/status/1558051450797690880
        - 'Project1' # DarkCloud - https://twitter.com/suyog41/status/1558051450797690880
        - 'DuckTales' # Racoon Stealer
        - 'Zadanie' # Racoon Stealer
        - 'GunnaWunnaBlueTips' # Racoon Stealer
        - 'Xlmst' # Racoon Stealer
        - 'GeekingToTheMoon' # Racoon Stealer
        - 'SunShineMoonLight' # Racoon Stealer
        - 'BunnyRequester' # BunnyStealer
        - 'BunnyTasks' # BunnyStealer
        - 'BunnyStealer' # BunnyStealer
        - 'BunnyLoader_Dropper' # BunnyStealer
        - 'BunnyLoader' # BunnyStealer
        - 'BunnyShell' # BunnyStealer
        - 'SPARK-COMMIT' # SparkRAT - https://arcticwolf.com/resources/blog/tellmethetruth-exploitation-of-cve-2023-46604-leading-to-ransomware/
        - '4B4DB4B3' # B4B3RAT - https://twitter.com/naumovax/status/1718956514491130301
        - 'SouthSide' # Racoon Stealer
        - 'Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Tob 1.1)' # Latrodectus loader
condition: selection

False positives (as the rule lists them)

Unknown

MITRE ATT&CK ids this rule names

T1071.001

References

http://rules.emergingthreats.net/open/snort-2.9.0/rules/emerging-user_agents.rules
http://www.botopedia.org/search?searchword=scan&searchphrase=all
https://networkraptor.blogspot.com/2015/01/user-agent-strings.html
https://perishablepress.com/blacklist/ua-2013.txt
https://www.bluecoat.com/en-gb/security-blog/2015-05-05/know-your-agents
https://twitter.com/kladblokje_88/status/1614673320124743681?s=12&t=joEpeVa5d58aHYNGA_To7Q
https://pbs.twimg.com/media/FtYbfsDXoAQ1Y8M?format=jpg&name=large
https://twitter.com/crep1x/status/1635034100213112833

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/web/proxy_generic/proxy_ua_malware.yml

Sources and licences

SigmaHQ
"Malware User Agent" by Florian Roth (Nextron Systems), X__Junior (Nextron Systems), Nasreddine Bencherchali (Nextron Systems) (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/web/proxy_generic/proxy_ua_malware.yml.
Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-License
Detection Rule License (DRL) 1.1

Cite this page

Dragons Eye Ransomware Tracker, "Sigma rule: Malware User Agent",
entity page, dataset version ref-c0d345fe9065, updated 2024-04-14T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/5c84856b-55a5-45f1-826f-13f37250cf4e (accessed 2026-11-03).
Underlying source: SigmaHQ rule 5c84856b-55a5-45f1-826f-13f37250cf4e, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.

Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.