A reported Free Download Manager supply chain attack redirected Linux users to a malicious Debian package repository that installed information-stealing malware.
The malware used in this campaign establishes a reverse shell to a C2 server and installs a Bash stealer that collects user data and account credentials.
Kaspersky discovered the potential supply chain compromise case while investigating suspicious domains, finding that the campaign has been underway for over three years.
FDM does some clever things to boost download speeds. It splits up a download into different chuncks, and somehow downloads them concurrently. It makes a big difference for large files (for example, Linux ISOs).
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I guess many servers are capping speeds them. Makes sense since I almost never see downloads actually take advantage of my Gigabit internet speeds.
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It could make multiple requests to the server, asking each request to resume starting at a certain byte.
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The key thing to know is that a client can do an HTTP
HEADrequest to get just theContent-Lengthof the file, and then performGETrequests with theRangerequest header to fetch a specific chunk of a file.This mechanism was introduced in HTTP 1.1 (byte-serving).
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