Csrss. Exe a Trojan Horse or Virus?

Csrss.exe process is a legitimate Windows process. It belongs to Client Server Runtime Subsystem, that carries several important functions in the operating system. The peculiarity of that process is that it is often counterfeited by viruses, primarily – by coin mining trojans¹. If you see in Task Manager that this process consumes more than 10% of your CPU, it is not ok. Read the article to know how to figure out the malware, and how to remove it from your PC.

Why does the csrss.exe process consume so much CPU capacity?

The legitimate process never takes more than 10% of your system power. Moreover, the functions csrss carries are usually performed when the user will likely not admit this. This process is responsible for correct data saving at the moments of logout/shutdown of the PC. Another, and less needed function is providing the console access for the apps at the moment of their startup². During the operations, the access is granted by another system process – conhost.exe.

If you have a performance problem and see that the csrss process has the lion’s share of CPU consumption, there is bad news for you. Your PC is likely infected with the coin miner virus or another dangerous malware that tries to stay unseen. Trojan-miner is a specific type of malware that performs quite a small amount of functions – it only mines cryptocurrency coins using your CPU and GPU. While you have no programs running, you will not fill any suspicious moments. But when you even try to start a browser – the troubles begin.

How dangerous csrss virus is?

The biggest damage can be dealt to mobile devices, i.e. laptops. This type of device is not designed to constantly cool the system if it works at 100% of its capacity. In a typical (for most laptop users) situation, when you have your device on your lap, you can unintentionally close the air intake holes, so the cooling will not serve properly. With luck, your laptop will just turn off due to the CPU throttling³. But some outdated systems, can have no throttling prevention mechanism, and such a strong overheating will surely lead to further CPU issues.

Desktop users will likely have less problems. But it is still an unpleasant experience to struggle with opening a browser window or to wait for a minute while Photoshop attempts to create a new layer. CPU miners don’t care about the user. Their target is to squeeze all possible coins from a single computer. The legit and familiar (at first sight) csrss process can spontaneously start to consume up to 90-95% of CPU power.