https://blogs.mcafee.com/mcafee-labs/meet-tox-ransomware-for-the-rest-of-us

Hunt Hypothesis

This hunt targets adversaries exhibiting Tox ransomware behavior by identifying specific file encryption patterns and lateral movement indicators typical of this “ransomware for the rest of us” strain. Proactively hunting for these signatures in Azure Sentinel is critical to validate low-severity alerts and ensure early detection before the malware escalates to a full-scale data exfiltration or encryption event.

YARA Rule

rule Win32Toxic : tox ransomware
{
meta:
	author = "@GelosSnake"
	date = "2015-06-02"
	description = "https://blogs.mcafee.com/mcafee-labs/meet-tox-ransomware-for-the-rest-of-us"
	hash0 = "70624c13be4d8a4c1361be38b49cb3eb"
	hash1 = "4f20d25cd3ae2e5c63d451d095d97046"
	hash2 = "e0473434cc83b57c4b579d585d4c4c57"
	hash3 = "c52090d184b63e5cc71b524153bb079e"
	hash4 = "7ac0b49baba9914b234cde62058c96a5"
	hash5 = "048c007de4902b6f4731fde45fa8e6a9"
	hash6 = "238ef3e35b14e304c87b9c62f18953a9"
	hash7 = "8908ccd681f66429c578a889e6e708e1"
	hash8 = "de9fe2b7d9463982cc77c78ee51e4d51"
	hash9 = "37add8d26a35a3dc9700b92b67625fa4"
	hash10 = "a0f30e89a3431fca1d389f90dba1d56e"
	hash11 = "d4d0658302c731003bf0683127618bd9"
	hash12 = "d1d89e1c7066f41c1d30985ac7b569db"
	hash13 = "97d52d7281dfae8ff9e704bf30ce2484"
	hash14 = "2cc85be01e86e0505697cf61219e66da"
	hash15 = "02ecfb44b9b11b846ea8233d524ecda3"
	hash16 = "703a6ebe71131671df6bc92086c9a641"
	hash17 = "df23629b4a4aed05d6a453280256c05a"
	hash18 = "07466ff2572f16c63e1fee206b081d11"
	hash19 = "792a1c0971775d32bad374b288792468"
	hash20 = "fb7fd5623fa6b7791a221fad463223cd"
	hash21 = "83a562aab1d66e5d170f091b2ae6a213"
	hash22 = "99214c8c9ff4653b533dc1b19a21d389"
	hash23 = "a92aec198eee23a3a9a145e64d0250ee"
	hash24 = "e0f7e6b96ca72b9755965b9dac3ce77e"
	hash25 = "f520fc947a6d5edb87aa01510bee9c8d"
	hash26 = "6d7babbe5e438539a9fa2c5d6128d3b4"
	hash27 = "3133c2231fcee5d6b0b4c988a5201da1"
	hash28 = "e5b1d198edc413376e0c0091566198e4"
	hash29 = "50515b5a6e717976823895465d5dc684"
	hash30 = "510389e8c7f22f2076fc7c5388e01220"
	hash31 = "60573c945aa3b8cfaca0bdb6dd7d2019"
	hash32 = "394187056697463eba97382018dfe151"
	hash33 = "045a5d3c95e28629927c72cf3313f4cd"
	hash34 = "70951624eb06f7db0dcab5fc33f49127"
	hash35 = "5def9e3f7b15b2a75c80596b5e24e0f4"
	hash36 = "35a42fb1c65ebd7d763db4abb26d33b0"
	hash37 = "b0030f5072864572f8e6ba9b295615fc"
	hash38 = "62706f48689f1ba3d1d79780010b8739"
	hash39 = "be86183fa029629ee9c07310cd630871"
	hash40 = "9755c3920d3a38eb1b5b7edbce6d4914"
	hash41 = "cb42611b4bed97d152721e8db5abd860"
	hash42 = "5475344d69fc6778e12dc1cbba23b382"
	hash43 = "8c1bf70742b62dec1b350a4e5046c7b6"
	hash44 = "6a6541c0f63f45eff725dec951ec90a7"
	hash45 = "a592c5bee0d81ee127cbfbcb4178afe8"
	hash46 = "b74c6d86ec3904f4d73d05b2797f1cc3"
	hash47 = "28d76fd4dd2dbfc61b0c99d2ad08cd8e"
	hash48 = "fc859ae67dc1596ac3fdd79b2ed02910"
	hash49 = "cb65d5e929da8ff5c8434fd8d36e5dfb"
	hash50 = "888dd1acce29cd37f0696a0284ab740a"
	hash51 = "0e3e231c255a5eefefd20d70c247d5f0"
	hash52 = "e5ebe35d934106f9f4cebbd84e04534b"
	hash53 = "3b580f1fa0c961a83920ce32b4e4e86d"
	hash54 = "d807a704f78121250227793ea15aa9c4"
	hash55 = "db462159bddc0953444afd7b0d57e783"
	hash56 = "2ed4945fb9e6202c10fad0761723cb0e"
	hash57 = "51183ab4fd2304a278e36d36b5fb990c"
	hash58 = "65d602313c585c8712ea0560a655ddeb"
	hash59 = "0128c12d4a72d14bb67e459b3700a373"
	hash60 = "5d3dfc161c983f8e820e59c370f65581"
	hash61 = "d4dd475179cd9f6180d5b931e8740ed6"
	hash62 = "5dd3782ce5f94686448326ddbbac934c"
	hash63 = "c85c6171a7ff05d66d497ad0d73a51ed"
	hash64 = "b42dda2100da688243fe85a819d61e2e"
	hash65 = "a5cf8f2b7d97d86f4d8948360f3db714"
	hash66 = "293cae15e4db1217ea72581836a6642c"
	hash67 = "56c3a5bae3cb1d0d315c1353ae67cf58"
	hash68 = "c86dc1d0378cc0b579a11d873ac944e7"
	hash69 = "54cef0185798f3ec1f4cb95fad4ddd7c"
	hash70 = "eb2eff9838043b67e8024ccadcfe1a8f"
	hash71 = "78778fe62ee28ef949eec2e7e5961ca8"
	hash72 = "e75c5762471a490d49b79d01da745498"
	hash73 = "1564d3e27b90a166a0989a61dc3bd646"
	hash74 = "59ba111403842c1f260f886d69e8757d"
	hash75 = "d840dfbe52a04665e40807c9d960cccc"
	hash76 = "77f543f4a8f54ecf84b15da8e928d3f9"
	hash77 = "bd9512679fdc1e1e89a24f6ebe0d5ad8"
	hash78 = "202f042d02be4f6469ed6f2e71f42c04"
	hash79 = "28f827673833175dd9094002f2f9b780"
	hash80 = "0ff10287b4c50e0d11ab998a28529415"
	hash81 = "644daa2b294c5583ce6aa8bc68f1d21f"
	hash82 = "1c9db47778a41775bbcb70256cc1a035"
	hash83 = "c203bc5752e5319b81cf1ca970c3ca96"
	hash84 = "656f2571e4f5172182fc970a5b21c0e7"
	hash85 = "c17122a9864e3bbf622285c4d5503282"
	hash86 = "f9e3a9636b45edbcef2ee28bd6b1cfbb"
	hash87 = "291ff8b46d417691a83c73a9d3a30cc9"
	hash88 = "1217877d3f7824165bb28281ccc80182"
	hash89 = "18419d775652f47a657c5400d4aef4a3"
	hash90 = "04417923bf4f2be48dd567dfd33684e2"
	hash91 = "31efe902ec6a5ab9e6876cfe715d7c84"
	hash92 = "a2e4472c5097d7433b91d65579711664"
	hash93 = "98854d7aba1874c39636ff3b703a1ed1"
	hash94 = "5149f0e0a56b33e7bbed1457aab8763f"
	hash95 = "7a4338193ce12529d6ae5cfcbb1019af"
	hash96 = "aa7f37206aba3cbe5e11d336424c549a"
	hash97 = "51cad5d45cdbc2940a66d044d5a8dabf"
	hash98 = "85edb7b8dee5b60e3ce32e1286207faa"
	hash99 = "34ca5292ae56fea78ba14abe8fe11f06"
	hash100 = "154187f07621a9213d77a18c0758960f"
	hash101 = "4e633f0478b993551db22afddfa22262"
	hash102 = "5c50e4427fe178566cada96b2afbc2d4"
	hash103 = "263001ac21ef78c31f4ca7ad2e7f191d"
	hash104 = "53fd9e7500e3522065a2dabb932d9dc5"
	hash105 = "48043dc55718eb9e5b134dac93ebb5f6"
	hash106 = "ca19a1b85363cfed4d36e3e7b990c8b6"
	hash107 = "41b5403a5443a3a84f0007131173c126"
	hash108 = "6f3833bc6e5940155aa804e58500da81"
	hash109 = "9bd50fcfa7ca6e171516101673c4e795"
	hash110 = "6d52ba0d48d5bf3242cd11488c75b9a7"
	hash111 = "c52afb663ff4165e407f53a82e34e1d5"
	hash112 = "5a16396d418355731c6d7bb7b21e05f7"
	hash113 = "05559db924e71cccee87d21b968d0930"
	hash114 = "824312bf8e8e7714616ba62997467fa8"
	hash115 = "dfec435e6264a0bfe47fc5239631903c"
	hash116 = "3512e7da9d66ca62be3418bead2fb091"
	hash117 = "7ad4df88db6f292e7ddeec7cf63fa2bc"
	hash118 = "d512da73d0ca103df3c9e7c074babc99"
	hash119 = "c622b844388c16278d1bc768dcfbbeab"
	hash120 = "170ffa1cd19a1cecc6dae5bdd10efb58"
	hash121 = "3a19c91c1c0baa7dd4a9def2e0b7c3e9"
	hash122 = "3b7ce3ceb8d2b85ab822f355904d47ce"
	hash123 = "a7bac2ace1f04a7ad440bd2f5f811edc"
	hash124 = "66594a62d8c98e1387ec8deb3fe39431"
	hash125 = "a1add9e5d7646584fd4140528d02e4c3"
	hash126 = "11328bbf5a76535e53ab35315321f904"
	hash127 = "048f19d79c953e523675e96fb6e417a9"
	hash128 = "eb65fc2922eafd62defd978a3215814b"
	hash129 = "51cc9987f86a76d75bf335a8864ec250"
	hash130 = "a7f91301712b5a3cc8c3ab9c119530ce"
	hash131 = "de976a5b3d603161a737e7b947fdbb9a"
	hash132 = "288a3659cc1aec47530752b3a31c232b"
	hash133 = "91da679f417040558059ccd5b1063688"
	hash134 = "4ce9a0877b5c6f439f3e90f52eb85398"
	hash135 = "1f9e097ff9724d4384c09748a71ef99d"
	hash136 = "7d8a64a94e71a5c24ad82e8a58f4b7e6"
	hash137 = "db119e3c6b57d9c6b739b0f9cbaeb6fd"
	hash138 = "52c9d25179bf010a4bb20d5b5b4e0615"
	hash139 = "4b9995578d51fb891040a7f159613a99"
	sample_filetype = "exe"
	yaragenerator = "https://github.com/Xen0ph0n/YaraGenerator"
strings:
	$string0 = "n:;;t:;;t:;;t:;;t:;;t:;;t:;;t:;;t:;;t:;;t:;;t:;;t:;;t;<<t;<<t;<<t;<<t;<<t;<<t;<<t;<<t<<<t;<<t;<<t;<<"
	$string1 = "t;<<t;<<t<<<t<<"
	$string2 = ">>><<<"
condition:
	2 of them
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 3 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Based on the behavior of Tox Ransomware described in the McAfee Labs blog—which specifically targets the mass creation of .tox files, the encryption of common document types, and the generation of ransom notes—here are 4 specific false positive scenarios in a legitimate enterprise environment:

• Scenario: Enterprise Backup Agent File Locking and Versioning

  • Context: Backup agents (e.g., Veeam, Commvault, or Rubrik) often perform incremental backups by creating temporary snapshots, locking files, and generating versioned copies before committing changes. If the backup agent processes a large volume of documents simultaneously, it may trigger file creation events that mimic Tox’s rapid .tox extension generation or mass file modification patterns.
  • Filter/Exclusion: Exclude the specific service accounts used by the backup solution (e.g., svc-veeam-backup, cvp-admin) and filter out processes running from the vendor’s installation directory (e.g., C:\Program Files\Veeam\Backup & Replication\). Additionally, exclude file operations where the destination path contains “Temp”, “Snapshot”, or “Version” keywords.

• Scenario: Scheduled Document Conversion via Office 365 ProPlus

  • Context: In environments with heavy document processing, scheduled tasks (e.g., running at 2:00 AM) may use Microsoft Word or Excel automation scripts to convert thousands of legacy documents into a standardized format. If the script saves converted files with specific extensions or creates temporary .tox-like placeholders during batch processing, this mass file activity can be misidentified as ransomware encryption behavior.
  • Filter/Exclusion: Create an exclusion for the WINWORD.EXE and EXCEL.EXE processes when running under the context of a specific scheduled task (e.g., “Batch_Doc_Con