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Expiro is a long-running Windows file-infector malware family that also functions as an information stealer and bot-capable backdoor. It infects 32-bit and 64-bit executable files by appending or inserting malicious code into host binaries, including cross-architecture infection in some variants, and can propagate by infecting executables on local, removable, and network drives. Expiro is notable for preserving host execution after its own payload runs, while using polymorphic infection logic and modifications to relocation data that complicate analysis, disinfection, and file repair. Some variants encrypt or alter relocation structures, making conventional repair routines unreliable and increasing the risk of file corruption during cleanup.
Beyond file infection, Expiro steals credentials and other sensitive data from browsers and applications, including email and FTP clients, and can capture web form submissions such as account, banking, and payment-card information. It has also been observed installing malicious browser extensions, lowering browser security settings, redirecting users, and harvesting confidential information entered into web sessions. Additional functionality includes theft of certificates and private keys, execution of shell commands, downloading and launching plugins, proxying, port forwarding, and TCP flood denial-of-service activity.
Expiro employs multiple defense-evasion measures, including anti-debugging and anti-analysis techniques, polymorphism, tampering with signed executables, disabling security services, and terminating selected security-related processes. Its ability to reinfect systems from any remaining infected executable makes eradication difficult in both home and enterprise environments. The malware has been active for more than a decade and remains one of the better-known Windows file infectors due to its combination of parasitic infection, credential theft, browser manipulation, and post-compromise bot functionality.
Mallory pivots from this family to the IOCs, detections, and named campaigns that touch your stack, and pages you when something new lands.
28 distinct techniques documented for this family, organized by ATT&CK tactic.
During the infection process, the virus will prepare this startup code for insertion into the specified file and some of these instructions will be overwritten, thus ensuring the uniqueness of the .vmp0 section contents (polymorphism).
The body of the virus in a 64-bit infected file is added to the end of the new section of the executable file, called .vmp0... To transfer control to the main body (.vmp0), the virus inserts 1,269 bytes of malicious startup code in place of the entry point.
The Expiro virus is unique in that it infiltrates executable files on both 32- and 64-bit Windows systems by appending its viral code to the host.
Expiro is a known file infector and information-stealer that hinders analysis with anti-debugging and anti-analysis tricks.
part of the code of content.js which performs parsing of form-elements on the web-page. Such an operation will help malicious code to retrieve data that has been entered by the user into forms
Cred Harvesting ... \FileZilla\sitemanager.xml INETCOMM Server Passwords Software\Microsoft\Internet Explorer\IntelliForms\Storage2
It can be used to install malicious browser extensions, lower browser security settings, and steal account credentials.
The malware also steals stored certificates and passwords from Internet Explorer... If a credit card form is present on a loaded web page, malware will try to steal data from it. | Expiro tries to steal FTP credentials from the FileZilla tool by loading info from %appdata%\FileZilla\sitemanager.xml.
Expiro is not innovative and uses an approach based on retrieving a list of processes, using API CreateToolhelp32Snapshot
the bot id for Gazavat is passed in the user agent ... same method used by DMSniff
start proxy server (SOCKS, HTTP); set port forwarding for TCP on the local router (SOAP).
The new variant, however, changes the size of the base relocation table and encrypts the addresses inside, causing traditional appender virus repair routines to corrupt files unless they correctly restore the original base relocation table.
the following code uses arithmetic obfuscation while passing an argument SERVICE_CONTROL_STOP (0x1) to advapi32!ControlService, using it to disable the service. | subsequent termination via OpenProcess / TerminateProcess. Expiro targets the following processes for termination: «MSASCui.exe», «msseces.exe» and «Tcpview.exe».
71 indicators attributed across vendor reports, sandbox runs, and researcher write-ups. Full values are available in Mallory.
IPs, domains, and DNS infrastructure linked to this family.
File hashes (MD5, SHA-1, SHA-256) from samples and reports.
7 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
Windows file-infector virus targeting executables, primarily to steal passwords from various programs.
Windows file-infector virus targeting executables, primarily to steal passwords for various programs.
Expiro is a virus that infects Windows systems, known for spreading and compromising files on the infected machine.
File-infector and information-stealing malware that employs anti-debugging and anti-analysis techniques to hinder investigation.
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.