nomadmag.blogg.se

1. Cobalt strike beacon names how to#
2. Cobalt strike beacon names full#
3. Cobalt strike beacon names series#

This method does require a process memory dump and encrypted data. If the decryption succeeds, a valid key has been found. All possible 16-byte long, non-null sequences found in process memory, will be used to try to decrypt a piece of encrypted C2 communication. To extract these keys, the method consists of performing a kind of dictionary attack. They are just 16-byte long sequences, without any distinguishable features. The AES and HMAC keys can be found in writable process memory, but there is no header that clearly identifies these keys. For these beacons, another method can be followed. And thus that is a false positive that must be ignored.įor Cobalt Strike version 4 beacons, it is very rare that the unencrypted metadata can be recovered from process memory. But that is not the case for the second instance (no recognizable names, no AES and HMAC keys found at other locations). And the AES and HMAC key extracted from that metadata, have also been found at other positions in process memory. This is the case for the example in figure 2: the first instance is indeed valid metadata, as it contains a recognizable machine name and username (look at Field: entries). Remark that tool cs-extract-key.py is likely to produce false positives: namely byte sequences that start with 0x0000BEEF, but are not actual metadata. These keys can then be used to decrypt the captured network traffic with tool cs-parse-http-traffic.py, like explained in Part 2. The first half of the SHA256 value is the HMAC key, and the second half is the AES key.

The AES and HMAC keys are derived from this raw key by calculating the SHA256 value of the raw key. The metadata contains the raw key: 16 random bytes. Tool cs-extract-key.py can be used to find and decode this metadata, like this: Figure 2: extracted and decoded metadata Figure 1: binary editor view of metadata in process memory The earlier in the lifespan of a process the process dump is taken, the more likely it is to contain the unencrypted metadata. This sequence is the header of the unencrypted metadata. dmp.įor Cobalt Strike version 3 beacons, the unencrypted metadata can often be found in memory by searching for byte sequence 0x0000BEEF. The process dump is stored inside a file with extension.

Cobalt strike beacon names full#

A full process memory dump is not required, a dump of all writable process memory is sufficient.Įxample of a command to produce a process dump of writable process memory: “procdump.exe -mp 1234”, where -mp is the option to dump writable process memory and 1234 is the process ID of the running beacon. One method to produce a process memory dump of a running beacon, is to use Sysinternals’ tool procdump. Another way to obtain the AES and HMAC key, is to extract them from the process memory of an active beacon. In part 2, we obtained these keys by decrypting the metadata with the private RSA key.

Cobalt strike beacon names how to#

In this blog post, we will explain how to decrypt Cobalt Strike traffic if you don’t know the private RSA key but do have a process memory dump.Ĭobalt Strike network traffic can be decrypted with the proper AES and HMAC keys. And in part 2, we decrypted Cobalt Strike traffic starting with a private RSA key. In part 1 of this series, we revealed private encryption keys found in rogue Cobalt Strike packages.

Cobalt strike beacon names series#

This series of blog posts describes different methods to decrypt Cobalt Strike traffic. We decrypt Cobalt Strike traffic with cryptographic keys extracted from process memory.