Understanding Userland Hooks and Rootkits in Real-World Investigations
- 12 hours ago
- 3 min read
Security improvements have made kernel rootkit techniques like (Import Address Table) IDT and SSDT hooks much harder for attackers to pull off. So, they’ve started looking for new ways—or sometimes, going back to old ones. One such method is userland hooking, which works in user mode instead of the kernel. That makes it less powerful but also harder to detect because legitimate applications use similar techniques all the time.
What Are Userland Hooks?
Userland hooks are ways for malware (or legit software) to intercept function calls in a program. Here are the two main types:
Import Address Table (IAT) Hooks: This is a simple trick where malware changes a function’s address in a process’s IAT, redirecting it to malicious code.
Inline/Trampoline Hooks: These modify the actual function code by inserting a jump instruction that leads to malware instead. These hooks are sneaky because they don’t mess with the IAT directly and only modify the function in memory.
For attackers, userland hooks are useful because they let them manipulate programs without triggering deep security defenses. Plus, they don’t have to mess with the kernel, where modern security tools are always watching.
Detecting Malicious Hooks
Using tools like Volatility’s apihooks plugin, you can find these hooks. But be warned—tons of legit software also use hooks, so you’ll need to separate the suspicious ones from the normal ones.
Some safe DLLs that are known to hook functions include:
• setupapi.dll
• mswsock.dll
• sfc_os.dll
• adsldpc.dll
• advapi32.dll
• secur32.dll
• ws2_32.dll
• iphlpapi.dll
• ntdll.dll
• kernel32.dll
• user32.dll
• gdi32.dll
Knowing which DLLs are commonly used by legitimate applications helps filter out false positives.
-------------------------------------------------------------------------------------------------------------
Digging Deeper with Driver Analysis
Malware often loads drivers to maintain deeper access to the system. Rootkits, in particular, use drivers to hide malicious activity.
The Volatility modules plugin helps list loaded drivers, while modscan scans memory for additional, possibly hidden drivers. These tools help you spot suspicious drivers, even if they’ve been unlinked from active memory structures.
---------------------------------------------------------------------------------------------------------------
You know identifying malicious drivers can be tricky—there are too many of them, and most analysts aren’t familiar with what should or shouldn’t be present.
To make thing easy for us I will use tool called Memory Baseliner
I have created an complete article related to Memory baseliner.
Now I will not explain what is this tool and what this tool. Check out the link above.
Finding Suspicious Drivers
In this case, I used Memory Baseliner with the --showknown and --imphash options.
Here’s why:
--showknown displays both known (baseline) and unknown (new) drivers.
--imphash calculates the import hash of drivers, making it easier to spot changes between versions.
A close-matching baseline image usually means only a handful of new drivers will appear.
Focus on those first, especially ones outside the usual \Windows\System32\Drivers and \Windows\System32 directories.
---------------------------------------------------------------------------------------------------------------
As an investigator, your job is to identify what’s normal and what’s suspicious.
Tools like Volatility’s apihooks, modules, modscan, and moddump are great for uncovering these threats.
Remember:
Just because something is hooked doesn’t mean it’s bad.
Look for unknown modules or drivers in memory.
Compare findings with clean systems to reduce false positives.
---------------------------------------------------------------------------------------------------------------
Rootkits: A Rare but Serious Threat
Rootkits are designed to hide processes, files, registry keys, and network artifacts. They aren’t as common as code injection, but they’re harder to detect.
Volatility 2 has some of the best memory analysis plugins for detecting rootkits by identifying process hooking and unlinking.
But here’s the challenge:
Many legitimate applications (like antivirus tools) use hooking too.
Only a tiny percentage of malware actually use rootkits.
Because of this, rootkit detection isn’t the first step in memory analysis. Instead, analysts typically discover them through:
Suspicious processes
Unexpected network connections
Unknown drivers
By the time you’re hunting for a rootkit, you’ve probably already found other indicators of compromise. The goal at this stage is to gather more evidence to understand the attack.
-------------------------------------------------------------------------------------------------------------
Wrapping Up
Memory Baseliner is a powerful tool for reducing the noise in memory analysis and quickly identifying unknown drivers.
As attackers continue to exploit vulnerabilities in drivers, security teams must stay ahead by integrating tools like Volatility, and Memory Baseliner into their workflows.
Keep hunting, keep learning, and most importantly—stay curious!
----------------------------------------------------------Dean-------------------------------------------
Yorumlar