Windows-based CLI susceptible to process injection attack

The fresh hacking technique could hide malware in legitimate apps

Hacking

Hackers could exploit a fresh process injection technique to conceal malware in a Windows-based CLI app

Rotem Kerner, a security researcher with cybersecurity firm enSilo, discovered and dubbed the technique "Ctrl-Inject". It abuses the Windows "CtrlRoutine" function, a function that provides the mechanism for handling Ctrl signals in console application.

Advertisement - Article continues below

Ctrl-Inject basically causes malicious threads to spawn inside the processes of legitimate CLI apps, which then allows malicious code to be run. 

Every time a user (or a process) sends Ctrl + C (or Break) signal to a console-based process (such as cmd.exe or powershell.exe), a system process called csrss.exe will invoke the function CtrlRoutine in a new thread on the targeted process.

"Essentially, in this process injection technique, we inject our code to the target process, but we never invoke it directly, that is, we never call CreateRemoteThread ourselves or alter execution flow using SetThreadContext. Instead, we are making csrss.exe invoke it for us which is far less suspicious since this a normal behaviour," said Kerner.

Among the applications that hackers could abuse are cmd.exe or powershell.exe, commonly found in most Windows systems. Normally, app processes can't be tampered with as Windows uses security protections such as Control Flow Guard and pointer encoding to verify such processes.

Advertisement
Advertisement - Article continues below
Advertisement - Article continues below

However, Kerner said in a blog post detailing the technical aspects of the flaw, that it was possible to bypass such protections.

Kerner said that a hacker could use the same function to create their own thread in a legitimate CLI app's process and run malware code. He said the main advantage of this technique over classic thread injection technique is that the remote thread is created by a trusted windows process, csrss.exe, which makes it much stealthier.

"The disadvantage is that it's limited to console application," he added.

Advertisement

Recommended

Visit/security/vulnerability/355236/hp-support-assistant-flaws-leave-windows-devices-open-to-attack
vulnerability

HP Support Assistant flaws leave Windows devices open to attack

6 Apr 2020
Visit/security/cyber-security/355234/safari-bug-let-hackers-access-cameras-on-iphones-and-macs
cyber security

Safari bug let hackers access cameras on iPhones and Macs

6 Apr 2020
Visit/software/video-conferencing/355229/zoom-we-moved-too-fast
video conferencing

Zoom CEO admits company "moved too fast" as privacy issues mount

6 Apr 2020
Visit/security/internet-security/355228/mozilla-fixes-two-firefox-zero-days-being-actively-exploited
internet security

Mozilla fixes two Firefox zero-days being actively exploited

6 Apr 2020

Most Popular

Visit/development/application-programming-interface-api/355192/apple-buys-dark-sky-weather-app-and-leaves
application programming interface (API)

Apple buys Dark Sky weather app and leaves Android users in the cold

1 Apr 2020
Visit/mobile/mobile-phones/355239/microsofts-patent-design-reveals-a-mobile-device-with-a-third-screen
Mobile Phones

Microsoft’s patent design reveals a mobile device with a third screen

6 Apr 2020
Visit/software/video-conferencing/355229/zoom-we-moved-too-fast
video conferencing

Zoom CEO admits company "moved too fast" as privacy issues mount

6 Apr 2020