#Cobalt strike beacon dll Patch
While prevention of intrusion is, of course, better than cure – identify your assets, patch them religiously, enforce MFA, restrict credentials, reduce AD attack paths, kill off those unused and poorly protected VPN accounts - detecting Cobalt Strike is Good Medicine and more attention needs to be on doing so. Its ubiquity is such that in late 2021 it even emerged Emotet malware now installs Cobalt Strike “beacons” (its payload to model an advanced actor, which executes PowerShell scripts, logs keystrokes, spawns other payloads, etc.).
#Cobalt strike beacon dll full
The product now has a full research and development team behind it – and hackers can’t get enough of it: Blue Teams need to pay close attention. The “threat emulation” framework ($3,500 per user for a year’s license, if bought commercially from owner Help Systems) was first released in 2012 by creator Raphael Mudge, who led its development until March 2021. Secureworks meanwhile found Cobalt Strike playing a role in 19% of the network intrusions it investigated in 2021. The &beacon_inline_execute function is Aggressor Script's entry point to run a BOF file.Cobalt Strike was the single most widely seen offensive tool used by Advanced Persistent Threat (APT) actors in the last quarters of 2021, according to analysis by security firm Trellix. A BOF is a good place to implement a lateral movement technique, an escalation of privilege tool, or a new reconaissance capability. You'll likely want to use Aggressor Script to run your finalized BOF implementations within Cobalt Strike. These decorations provide the compiler with the needed hints to pass arguments and generate the right call instruction. Keywords, such as WINAPI and DECLSPEC_IMPORT are important.
When you declare function prototypes for Dynamic Function Resolution, pay close attention to the decorators attached to the function declaration.
#Cobalt strike beacon dll code
The above code makes DFR calls to DsGetDcNameA and NetApiBufferFree from NETAPI32. Here's an example BOF that uses DFR and looks up the current domain: #include ĭECLSPEC_IMPORT DWORD WINAPI NETAPI32$DsGetDcNameA(LPVOID, LPVOID, LPVOID, LPVOID, ULONG, LPVOID) ĭECLSPEC_IMPORT DWORD WINAPI NETAPI32$NetApiBufferFree(LPVOID) ĭwRet = NETAPI32$DsGetDcNameA(NULL, NULL, NULL, NULL, 0, &pdcInfo) īeaconPrintf(CALLBACK_OUTPUT, "%s", pdcInfo->DomainName) When this process fails, Cobalt Strike will refuse to execute the BOF and tell you which function it couldn't resolve. This convention provides Beacon the information it needs to explicitly resolve the specific function and make it available to your BOF file before it runs.
Another option is to use Dynamic Function Resolution (DFR).ĭynamic Function Resolution is a convention to declare and call Win32 APIs as LIBRARY$Function. You have the option to use these to resolve Win32 APIs you wish to call. GetProcAddress, LoadLibraryA, GetModuleHandle, and FreeLibrary are available within BOF files. BeaconOutput is an internal Beacon API to send output to the operator. It's the function that's called by inline-execute and arguments are passed to it. The function go is similar to main in any other C program. Use inline-execute in Beacon to run the BOF.īeacon> inline-execute /path/to/hello.o these are argumentsīeacon.h contains definitions for several internal Beacon APIs. The above commands will produce a hello.o file. The same exploit, built as a BOF, is īeaconPrintf(CALLBACK_OUTPUT, "Hello World: %s", args) A UAC bypass privilege escalation Reflective DLL implementation may weigh in at 100KB+. They run inside of a Beacon process and are cleaned up after the capability is done.īOFs are also very small. These tools rely on an OPSEC expensive fork&run pattern that involves a process create and injection for each post-exploitation action. Cobalt Strike already has tools to use PowerShell. One of the key roles of an command&control platform is to provide ways to use external post-exploitation functionality. Way to rapidly extend the Beacon agent with new post-exploitation features.
A Beacon Object File (BOF) is a compiled C program, written to a convention that allows it to execute within a Beacon process and use internal Beacon APIs.