Thursday, February 16, 2017

Cerber payload generator with different hashes

@MlwrHpstr posted a cerber url


If you go directly to the link it'll download a file

If you run md5sum on the file you'll get a hash


If you search that md5 on virus total

Which shows you some interesting details about it

If you run strings you'll see this is no php file, this is no .gif file, this is a windows executable

Something else interesting is that this web server read.php script is setup to only serve certain parameter values. If you try to pass in something like 2.gif instead of 1.gif you get an http 200 but no file.

If you try to leave the f parameter empty, you actually get a file but it's 0 bytes and empty

Thus I would venture to guess there are other parameter values you could pass that may serve up different payloads.

Also if you go to the root of the site they have it redirecting to so this is not a compromised site, it's simply a site setup with malicious purposes to serve certain hidden payloads.

If you type in any random php page name that doesn't exist you'll be able to tell the web server version it's running ( Apache/2.2.15 (CentOS) Server )

Poking around found another page that works (admin.php instead of read.php)

Which delivers a different payload with different hash ( 6ab4bfd0fa555fc570188af13409a669 ) which gives different virus total hits, another EXE

Actually it's interesting, this php file generates random cerber EXEs with different hashes every time you re-load it.

Good example of why signature based tools like AV are dying, because of stuff like this that is probably the same exact payload just slightly modified so that the hash changes every time.

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