MalwareUsed by 1 actor

Remexi

Remexi is a custom Windows backdoor used by the Iran-linked cyberespionage group Chafer, also known as APT39. It supports remote command execution and surveillance of compromised systems, including keystroke logging, clipboard text collection, screenshots of selected windows, and retrieval of active-window titles. It also collects system usernames for victim reconnaissance.

Remexi uses AutoIt and VBScript during execution and can execute operator-supplied WMI commands through the Windows Management Instrumentation command-line utility. It establishes persistence through scheduled tasks and machine-wide registry autostart mechanisms. Its configuration is protected with XOR encryption using 25-character keys. Command-and-control communications and data exfiltration use BITSAdmin, allowing collected information to leave the system over the same channel used for operator communications.

Remexi forms part of Chafer's espionage toolset. The group's targeting has included telecommunications, aviation, travel-related businesses, and government organizations, particularly in the Middle East.

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THREAT ACTORS

Groups observed using it

1 distinct threat actor attributed by public researchers. Open in Mallory to see the full evidence chain and overlapping campaigns.

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APT39

Found as “mas.dll” in our telemetry, it has been previously depicted as a backdoor.

via bitdefender labsbitdefender.com

MITRE ATT&CK

Techniques & procedures

17 distinct techniques documented for this family, organized by ATT&CK tactic.

Execution

4 techniques

T1047Windows Management InstrumentationEvidence2

T1053.005Scheduled TaskEvidence3

The content repeatedly describes malware and threat actors creating, modifying, or invoking Windows scheduled tasks via Task Scheduler or schtasks for persistence, execution, and lateral movement.

T1059.003Windows Command ShellEvidence3

The content repeatedly describes threat actors and malware using cmd.exe, the Windows command shell, to execute commands, launch payloads, run batch files, and automate actions on compromised hosts.

T1059.005Visual BasicEvidence3

APT-C-36 has embedded a VBScript within a malicious Word document which is executed upon the document opening.

Persistence

3 techniques

T1053.005Scheduled TaskEvidence3

The content repeatedly describes malware and threat actors creating, modifying, or invoking Windows scheduled tasks via Task Scheduler or schtasks for persistence, execution, and lateral movement.

T1547.001Registry Run Keys / Startup FolderEvidence5

The content repeatedly describes malware and threat actors establishing persistence by adding values under Registry Run keys such as HKCU\Software\Microsoft\Windows\CurrentVersion\Run and HKLM\Software\Microsoft\Windows\CurrentVersion\Run, and by placing shortcuts or files in Startup folders.

T1547.004Winlogon Helper DLLEvidence2

Privilege Escalation

3 techniques

T1053.005Scheduled TaskEvidence3

The content repeatedly describes malware and threat actors creating, modifying, or invoking Windows scheduled tasks via Task Scheduler or schtasks for persistence, execution, and lateral movement.

T1547.001Registry Run Keys / Startup FolderEvidence5

T1547.004Winlogon Helper DLLEvidence2

Stealth

2 techniques

T1027.013Encrypted/Encoded FileEvidence2

T1140Deobfuscate/Decode Files or InformationEvidence5

The content is a long ATT&CK-style listing of malware and threat groups that 'decrypt', 'decode', 'deobfuscate', 'unpack', or 'decompress' payloads, strings, configuration data, shellcode, and files prior to execution or use.

Credential Access

1 technique

T1056.001KeyloggingEvidence3

The content is a catalog of malware families and threat actors that 'can perform keylogging,' 'log keystrokes,' 'capture keystrokes,' or use 'keylogger' modules/tools.

Discovery

3 techniques

T1010Application Window DiscoveryEvidence2

T1033System Owner/User DiscoveryEvidence2

The content repeatedly describes malware and threat actors collecting the victim username, identifying logged-in users, running whoami, query user, quser, or similar commands to determine the current user or user sessions.

T1083File and Directory DiscoveryEvidence4

The content is a long ATT&CK-style listing of groups and malware that can 'list files and directories,' 'search for files,' 'enumerate drives,' 'gather file metadata,' or 'browse file systems' on compromised hosts.

Collection

4 techniques

T1056.001KeyloggingEvidence3

The content is a catalog of malware families and threat actors that 'can perform keylogging,' 'log keystrokes,' 'capture keystrokes,' or use 'keylogger' modules/tools.

T1113Screen CaptureEvidence4

The content is a MITRE ATT&CK-style listing of malware and threat actors that "can capture screenshots," "take screenshots," "perform screen captures," or "watch the victim's screen." It ends with references to "CopyFromScreen" and "xwd."

T1115Clipboard DataEvidence3

Agent Tesla can steal data from the victim’s clipboard. APT38 used a Trojan called KEYLIME to collect data from the clipboard. APT39 has used tools capable of stealing contents of the clipboard.

T1560Archive Collected DataEvidence2

Command and Control

1 technique

T1071.001Web ProtocolsEvidence2

Exfiltration

1 technique

T1041Exfiltration Over C2 ChannelEvidence3

ADVSTORESHELL exfiltrates data over the same channel used for C2.

INDICATORS OF COMPROMISE

IOCs tracked for this family

1 indicator attributed across vendor reports, sandbox runs, and researcher write-ups. Full values are available in Mallory.

View more in app

Hashes

1 tracked

File hashes (MD5, SHA-1, SHA-256) from samples and reports.

TypeValueLatest sighting

hash.sha256●●●●●●●●●●●●View more in app—

ACTIVITY FEED

Recent activity

44 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

44 SOURCESView more in app

symantec enterprise blogsNews

Jul 16, 2026

Latest U.S. Indictments Target Iranian Espionage Actors | SECURITY.COM

Backdoor malware explicitly listed by Symantec as associated with Chafer attack protections.

mitre attack websiteNews

Oct 25, 2022

System Owner/User Discovery, Technique T1033 - Enterprise | MITRE ATT&CK®

Backdoor used to collect usernames from the system.

mitre attack websiteNews

Oct 25, 2022

Command and Scripting Interpreter: Visual Basic, Sub-technique T1059.005 - Enterprise | MITRE ATT&CK®

Uses AutoIt and VBS scripts throughout execution.

mitre attack websiteNews

Oct 21, 2021

Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder, Sub-technique T1547.001 - Enterprise | MITRE ATT&CK®

Malware that establishes persistence via HKLM Run registry keys.

+40 more in the timeline

What this page doesn’t show

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IOC matching1

Match every observed IP, domain, and hash against your live telemetry.

Threat actor attribution1

Named campaigns wielding this family, with evidence pinned to each claim.

Exploited vulnerabilities

CVEs this family uses for access and lateral movement.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

MITRE ATT&CK mapping17

Every documented technique, ranked by evidence weight.

Researcher chatter

Reddit, Mastodon, and CTI community discussion around this family.

Remexi