FIN13 (also tracked as ElephantBeetle and SQUAB SPIDER) is a financially-motivated actor performing targeted intrusions against financial institutions in Mexico and Latin America dating back to 2016. Rather than using commodity malware such as CobaltStrike and some Ransomware-as-a-Service binary, they make heavy use of custom tooling such as webshells to tunnel network traffic before monetising their intrusion through data theft and injection of fraudulent transactions into payment systems. This series of rules covers the custom tools attributed to FIN13 in this Mandiant blog post.
LATCHKEY is a PowerShell to EXE (PS2EXE) compiled dropper that base64 decodes and executes the PowerSploit function Out-Minidump which generates a minidump for the LSASS system process to disk.
FIN13: A Cybercriminal Threat Actor Focused on Mexico
rule MAL_FIN13_LATCHKEY {
meta:
description = "Matches strings found in LATCHKEY ps2exe loader used by FIN13 (AKA: ElephantBeetle, SQUAB SPIDER)"
last_modified = "2024-04-03"
author = "@petermstewart"
DaysofYara = "94/100"
sha256 = "b23621caf5323e2207d8fbf5bee0a9bd9ce110af64b8f5579a80f2767564f917"
ref = "https://www.mandiant.com/resources/blog/fin13-cybercriminal-mexico"
strings:
$a1 = "Unhandeled exception in PS2EXE" wide
$b1 = "function Out-Minidump" base64wide
$b2 = "$MiniDumpWriteDump = $WERNativeMethods.GetMethod('MiniDumpWriteDump', $Flags)" base64wide
$b3 = "Get-Process lsass | Out-Minidump" base64wide
condition:
filesize < 50KB and
uint16(0) == 0x5a4d and
all of them
}
Find the rest of my 100DaysofYARA posts here, and the rules themselves on my Github repository.
Cyber Poking 