RainyDay
RainyDay is a backdoor associated with the Firefly group, also known as Naikon. Reported capabilities include collecting credentials from web browsers, capturing screenshots, using TCP for command-and-control communications, and leveraging proxy tooling such as boost_proxy_client for reverse proxy functionality. It can establish persistence via scheduled tasks and can also create and register a Windows service for execution. Execution has also been observed via side-loading of malicious executables. For data theft, RainyDay can stage files in C:\ProgramData\Adobe\temp prior to exfiltration and can use a file exfiltration tool to upload specific files to Dropbox. It has used filenames intended to mimic legitimate software, including vmtoolsd.exe to spoof VMware Tools. The content also notes that a newer variant has features overlapping both the RainyDay and Turian backdoors.
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Groups observed using it
4 distinct threat actors attributed by public researchers. Open in Mallory to see the full evidence chain and overlapping campaigns.
The new variant's features overlap with both the RainyDay and Turian backdoors...
The new variant's features overlap with both the RainyDay and Turian backdoors...
Techniques & procedures
24 distinct techniques documented for this family, organized by ATT&CK tactic.
Execution
5 techniques“Sandworm Team leveraged Scheduled Tasks through a Group Policy Object (GPO) to execute CaddyWiper at a predetermined time.” / “APT29 used scheduler and schtasks to create new tasks on remote host as part of their lateral movement… updating an existing legitimate task to execute their tools and then returned the scheduled task to its original configuration.”
During the 2022 Ukraine Electric Power Attack, Sandworm Team leveraged Scheduled Tasks through a Group Policy Object (GPO) to execute CaddyWiper at a predetermined time.
During the 2016 Ukraine Electric Power Attack, Sandworm Team used the xp_cmdshell command in MS-SQL. During the 2025 Poland Wiper Attacks, the adversaries leveraged PsExec to run cmd.exe commands on multiple victim machines. Numerous malware families and groups are described as using cmd.exe, cmd /c, Windows command shell, or command-line interfaces to execute commands, payloads, reconnaissance, persistence, cleanup, and ransomware actions.
"A version of the legitimate VLC Media Player masquerading as a Google file (googleupdate.exe) was used to sideload a Coolclient loader (file name: libvlc.dll)." / "The loader is sideloaded using a legitimate F-Secure executable named fsstm.exe." / "It is sideloaded using an executable called msproxy.exe..."
Persistence
3 techniques“Sandworm Team leveraged Scheduled Tasks through a Group Policy Object (GPO) to execute CaddyWiper at a predetermined time.” / “APT29 used scheduler and schtasks to create new tasks on remote host as part of their lateral movement… updating an existing legitimate task to execute their tools and then returned the scheduled task to its original configuration.”
During the 2022 Ukraine Electric Power Attack, Sandworm Team leveraged Scheduled Tasks through a Group Policy Object (GPO) to execute CaddyWiper at a predetermined time.
“Sandworm Team used an arbitrary system service to load at system boot for persistence for Industroyer… replaced the ImagePath registry value of a Windows service with a new backdoor binary… [multiple groups/malware] creating a service / installing as a service / modifying service configurations for persistence.”
Privilege Escalation
3 techniques“Sandworm Team leveraged Scheduled Tasks through a Group Policy Object (GPO) to execute CaddyWiper at a predetermined time.” / “APT29 used scheduler and schtasks to create new tasks on remote host as part of their lateral movement… updating an existing legitimate task to execute their tools and then returned the scheduled task to its original configuration.”
During the 2022 Ukraine Electric Power Attack, Sandworm Team leveraged Scheduled Tasks through a Group Policy Object (GPO) to execute CaddyWiper at a predetermined time.
“Sandworm Team used an arbitrary system service to load at system boot for persistence for Industroyer… replaced the ImagePath registry value of a Windows service with a new backdoor binary… [multiple groups/malware] creating a service / installing as a service / modifying service configurations for persistence.”
Stealth
7 techniquesThe content repeatedly describes payloads, strings, configuration files, scripts, URLs, and binaries being obfuscated or encoded using Base64, XOR, RC4, AES, RSA, hex encoding, custom algorithms, and other methods across many malware families and threat actors.
Examples throughout the content include 'encrypted payloads decrypted and executed in memory,' 'encrypts its configuration file,' 'AES-encrypted resource,' 'RC4 encrypted embedded scripts,' and 'payload includes an encrypted main component.'
During the 2016 Ukraine Electric Power Attack, DLLs and EXEs with filenames associated with common electric power sector protocols were used to masquerade files.
Akira has used legitimate names and locations for files to evade defenses.
The content repeatedly describes threat actors and malware deleting files, tools, scripts, logs, droppers, staged data, and artifacts from compromised systems to cover tracks, remove evidence, or self-delete.
The content repeatedly describes malware and threat actors decoding, decrypting, or deobfuscating payloads, strings, configuration data, commands, and C2 traffic prior to execution or use, e.g., 'APT28 macro uses the command certutil -decode to decode contents of a .txt file storing the base64 encoded payload' and 'Action RAT can use Base64 to decode actor-controlled C2 server communications.'
"A version of the legitimate VLC Media Player masquerading as a Google file (googleupdate.exe) was used to sideload a Coolclient loader (file name: libvlc.dll)." / "The loader is sideloaded using a legitimate F-Secure executable named fsstm.exe." / "It is sideloaded using an executable called msproxy.exe..."
Credential Access
1 techniqueThe content repeatedly describes threat actors and malware stealing usernames, passwords, cookies, session tokens, and other saved credentials from web browsers such as Chrome, Firefox, Internet Explorer, Edge, Opera, Safari, and Yandex.
Discovery
3 techniques"actors used the following command ... to obtain information about services: net start"; "APT1 used the commands net start and tasklist to get a listing of the services on the system"; "OilRig has used sc query on a victim to gather information about services"; "Indrik Spider has used the win32_service WMI class to retrieve a list of services"
The content repeatedly describes malware and threat actors obtaining lists of running processes, using utilities such as tasklist, ps, WMI, Get-Process, CreateToolhelp32Snapshot, EnumProcesses, and similar APIs/commands to enumerate active processes on victim systems.
BADNEWS crawls the victim's local drives and collects documents with selected extensions; Machete searches the file system for files of interest; Rover searches for files on local drives based on a predefined list of file extensions.
Collection
3 techniquesThe content repeatedly describes threat actors and malware collecting, stealing, identifying, copying, or staging files, documents, credentials, logs, databases, and other information from compromised hosts or local systems.
The content repeatedly describes adversaries and malware storing collected data, command output, credentials, archives, or files in local temporary folders, working directories, hidden directories, registry locations, recycle bins, or specific files prior to exfiltration.
"Agent Tesla can capture screenshots of the victim’s desktop"; "AppleSeed can take screenshots on a compromised host"; "APT28 has used tools to take screenshots from victims"; "Cobalt Strike's Beacon payload is capable of capturing screenshots"; "PowerSploit's Get-TimedScreenshot Exfiltration module can take screenshots at regular intervals"; "Hydraq includes a component based on the code of VNC that can stream a live feed of the desktop"
Command and Control
4 techniquesThe content repeatedly describes threat actors, malware, and campaigns using HTTP and/or HTTPS for command and control, including examples such as BlackEnergy communicating with C2 over HTTP POST requests and many other families using HTTP/S for C2.
"APT41 used a tool called CLASSFON to covertly proxy network communications." / "BADCALL functions as a proxy server between the victim and C2 server." / "Sandworm Team's BCS-server tool can create an internal proxy server to redirect traffic..."
Exfiltration
1 techniqueAkira will exfiltrate victim data using applications such as Rclone. APT41 DUST exfiltrated collected information to OneDrive. BoomBox can upload data to dedicated per-victim folders in Dropbox. During C0015, the threat actors exfiltrated files and sensitive data to the MEGA cloud storage site using the Rclone command.
Recent activity
33 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
Backdoor whose configuration structure is reused by the described PlugX variant; delivered via DLL side-loading and executed in-memory in the described attack chain.
Enterprise New Software: ... RainyDay
Malware/tool used to upload selected files to Dropbox for exfiltration.
Backdoor that achieves persistence via scheduled tasks.
The version that knows your environment.
Match every observed IP, domain, and hash against your live telemetry.
Named campaigns wielding this family, with evidence pinned to each claim.
CVEs this family uses for access and lateral movement.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Every documented technique, ranked by evidence weight.
Reddit, Mastodon, and CTI community discussion around this family.