Webhook Exfil

Description

A Discord webhook allows an external service to send automated messages or notifications directly to a specific channel in a Discord server. This is a commonly used exfiltration technique used by a lot of recent stealer malware.

Importance

Discovering a hard-coded webhook within an open-source software package is an indication of potential malicious activity. When combined with a POST request to that webhook, it is highly likely to be a variant of credential-stealing malware. It's worth noting that most stealers are intended to operate during package installation. This means that if a user were to execute a pip install <package> command in the case of PyPI, the malware would be triggered, making it critical to be aware of any attempts at webhook exfiltration before installing the package.

Examples

The use of a Discord webhook as a method for data exfiltration is a relatively new technique that has been widely observed and previously documented in publications. Generally, these stealers are activated during package installation and easily spotted by a cursory glance at the code. However, in March 2023, Phylum released an article outlining how attackers are now utilizing this method in a more subtle manner by concealing the stealer code deep within existing packages.