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.
NIGHTJAR is a Java-based file upload tool observed by Mandiant in multiple FIN13 intrusions.
rule MAL_FIN13_NIGHTJAR {
meta:
description = "Matches strings found in NIGHTJAR file upload tool used by FIN13 (AKA: ElephantBeetle, SQUAB SPIDER)"
last_modified = "2024-04-06"
author = "@petermstewart"
DaysofYara = "97/100"
sha256 = "5ece301c0e0295b511f4def643bf6c01129803bac52b032bb19d1e91c679cacb"
ref = "https://www.mandiant.com/resources/blog/fin13-cybercriminal-mexico"
strings:
$a1 = "org/eclipse/jdt/internal/jarinjarloader/RsrcURLConnection.class"
$a2 = "org/eclipse/jdt/internal/jarinjarloader/RsrcURLStreamHandler.class"
$a3 = "org/eclipse/jdt/internal/jarinjarloader/RsrcURLStreamHandlerFactory.class"
$a4 = "FileTransferClient.class"
condition:
filesize < 15KB and
uint16(0) == 0x4b50 and
all of them
}
Find the rest of my 100DaysofYARA posts here, and the rules themselves on my Github repository.
Cyber Poking 