S1035: Small Sieve
Small Sieve is a Telegram Bot API-based Python backdoor that has been distributed using a Nullsoft Scriptable Install System (NSIS) Installer; it has been used by MuddyWater since at least January 2022.[1][2]
Security researchers have also noted Small Sieve's use by UNC3313, which may be associated with MuddyWater.[3]
Security context for executives and security teams
S1035: Small Sieve describes [Small Sieve](https://attack.mitre.org/software/S1035) is a Telegram Bot API-based Python backdoor that has been distributed using a Nullsoft Scriptable Install System (NSIS) Installer; it has been used by [MuddyWater](https://attack.mitre.org/groups/G0069) since at least January 2022.(Citation: DHS CISA AA22-055A MuddyWater February 2022)(Citation: NCSC GCHQ Small Sieve Jan 2022) Security researchers have also noted [Small Sieve](https://attack.mitre.org/software/S1035)'s use by UNC3313, which may be associated wi...
Executive priority
S1035: Small Sieve is an official MITRE ATT&CK software. Glexia treats it as defensive behavior context for prioritizing monitoring, control validation, and response planning without using the object by itself as an attribution claim.
Technical view
Security teams should validate S1035: Small Sieve by reviewing the official ATT&CK relationships, mapped tactics (the mapped ATT&CK tactic context), supported platforms (Windows), and available local telemetry before making detection or mitigation decisions.
Likely telemetry
- Official ATT&CK relationships and object metadata
- Network, endpoint, and security-tool telemetry
Detection direction
- Validate whether S1035: Small Sieve appears in your detection coverage and tabletop scenarios.
- Use the object to align executive risk language with SOC, incident response, and detection engineering work.
- Do not treat ATT&CK relationship context as attribution without corroborating evidence.
Mitigation priorities
- Map the object to existing controls and identify missing telemetry or response ownership.
- Prioritize mitigations that reduce exposure on the listed platforms and tactics.
- Review adjacent ATT&CK relationships before changing policy, detections, or reporting language.
Additional notes and limits
Baseline Glexia take generated from the official MITRE ATT&CK STIX object, source hash, tactics, platforms, and detection fields. It is safe to replace with a richer model-generated take for the same source hash later.
This baseline take is source-grounded and schema-validated, but it does not include environment-specific telemetry, incident evidence, or threat-intelligence corroboration.
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Small Sieve
Small Sieve is a Telegram Bot API-based Python backdoor that has been distributed using a Nullsoft Scriptable Install System (NSIS) Installer; it has been used by MuddyWater since at least January 2022.[1][2]
Security researchers have also noted Small Sieve's use by UNC3313, which may be associated with MuddyWater.[3]
How security teams should use this page
Treat this object as behavior context, not an attribution claim. Validate the related groups, software, data sources, and mitigations against official ATT&CK relationships and your own telemetry before making control-coverage decisions.
Techniques used
This mirrors the MITRE pattern of making group, software, campaign, and technique relationships scannable. Relationship notes come from mirrored ATT&CK relationship text when available.
| Domain | ID | Name | Relationship / procedure |
|---|---|---|---|
| Enterprise | T1059.003 | Windows Command ShellSub-technique | Small Sieve can use `cmd.exe` to execute commands on a victim's system.[2] |
| Enterprise | T1105 | Ingress Tool Transfer | Small Sieve has the ability to download files.[2] |
| Enterprise | T1132.002 | Non-Standard EncodingSub-technique | Small Sieve can use a custom hex byte swapping encoding scheme to obfuscate tasking traffic.[1][2] |
| Enterprise | T1480 | Execution Guardrails | Small Sieve can only execute correctly if the word `Platypus` is passed to it on the command line.[2] |
| Enterprise | T1016 | System Network Configuration Discovery | Small Sieve can obtain the IP address of a victim host.[2] |
| Enterprise | T1573.002 | Asymmetric CryptographySub-technique | Small Sieve can use SSL/TLS for its HTTPS Telegram Bot API-based C2 channel.[1] |
| Enterprise | T1059.006 | PythonSub-technique | Small Sieve can use Python scripts to execute commands.[2] |
| Enterprise | T1547.001 | Registry Run Keys / Startup FolderSub-technique | Small Sieve has the ability to add itself to `HKCU\Software\Microsoft\Windows\CurrentVersion\Run\OutlookMicrosift` for persistence.[2] |
| Enterprise | T1036.005 | Match Legitimate Resource Name or LocationSub-technique | Small Sieve can use variations of Microsoft and Outlook spellings, such as "Microsift", in its file names to avoid detection.[2] |
| Enterprise | T1027 | Obfuscated Files or Information | Small Sieve has the ability to use a custom hex byte swapping encoding scheme combined with an obfuscated Base64 function to protect program strings and Telegram credentials.[2] |
| Enterprise | T1033 | System Owner/User Discovery | Small Sieve can obtain the id of a logged in user.[2] |
| Enterprise | T1102.002 | Bidirectional CommunicationSub-technique | Small Sieve has the ability to use the Telegram Bot API from Telegram Messenger to send and receive messages.[2] |
| Enterprise | T1071.001 | Web ProtocolsSub-technique | Small Sieve can contact actor-controlled C2 servers by using the Telegram API over HTTPS.[1] |
Groups, software, and campaigns
G0069: MuddyWater
MuddyWater is a cyber espionage group assessed to be a subordinate element within Iran's Ministry of Intelligence and Security (MOIS).[1] Since at least 2017, MuddyWater has targeted a range of government and private organizations across sectors, including telecommunications, local government, finance, defense, and oil and natural gas organizations, in the Middle East (specifically the UAE and Saudi Arabia), Asia, Africa, Europe, and North America. MuddyWater has reused domains dating back to October 2025, and has a preference for NameCheap and Hosterdaddy Private Limited (AS136557). In late 2025 and early 2026, MuddyWater used commercial satellite internet (i.e., Starlink) for command and control (C2) communication. [2][3][4][5][6][7][8][9][10][11][12][13]
All related ATT&CK context
Object version and sync metadata
The fields below describe the current mirrored snapshot. When Glexia retains multiple ATT&CK source imports, you can open the table to compare the same object across releases (hashes and MITRE timestamps). For MITRE’s own release notes and roadmap, see ATT&CK resources — Updates.
Imported snapshots across ATT&CK releases(2)
| Release | Bundle imported | Object version | Modified | Status | Raw hash |
|---|---|---|---|---|---|
| 19.2 | 1.0 | Current bundle | 956f2959222f… | ||
| 19.1 | 1.0 | Older bundle | 956f2959222f… |
Mirrored ATT&CK source object
The raw object is retained through the mirrored ATT&CK source bundle and object hash. The raw endpoint returns the exact object from the mirrored bundle when available.
External references and citations
MITRE external references are preserved separately from Glexia analysis so citations remain traceable to their original source records.
- [1]DHS CISA AA22-055A MuddyWater February 2022
FBI, CISA, CNMF, NCSC-UK. (2022, February 24). Iranian Government-Sponsored Actors Conduct Cyber Operations Against Global Government and Commercial Networks. Retrieved September 27, 2022.
Open source URL - [2]NCSC GCHQ Small Sieve Jan 2022
NCSC GCHQ. (2022, January 27). Small Sieve Malware Analysis Report. Retrieved August 22, 2022.
Open source URL - [3]Mandiant UNC3313 Feb 2022
Tomcik, R. et al. (2022, February 24). Left On Read: Telegram Malware Spotted in Latest Iranian Cyber Espionage Activity. Retrieved August 18, 2022.
Open source URL - [4]GRAMDOOR
(Citation: Mandiant UNC3313 Feb 2022)
- [5]mitre-attackS1035Open source URL
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