Maintaining access using vulnerabilities in common software

The DLL search order hijacking/DLL planting technique is one of my favorite persistence-gaining methods in achieving long-time access while evading the eyes of the administrators. Let's talk about this technique in the next section.

DLL search order hijacking

As the name suggests, the DLL search order hijacking vulnerability allows an attacker to hijack the search order of DLLs loaded by a program and will enable them to insert a malicious DLL instead of a legit one.

Mostly, software, once executed, will look for DLL files in its current folder and System32 folder. However, sometimes the DLLs, which are not found in its current directory, are then searched in the System32 folder instead of directly loading them from System32 first-hand. This situation can be exploited by an attacker where they can put a malicious DLL file in the current folder and hijack the flow which would have otherwise loaded the DLL from the System32 folder. Let...