Computers do not work easily with truly random numbers and it pays off to understand how pseudo-random numbers are used and created. Malware has two main uses that most malware has for random number generators, encryption and filename creation. With encryption, be it file encryption or network traffic encryption, malware can use a custom or built-in PRNG and use a unique seed found by obtaining specific system variables, such as the ID number for your hard drive or, as mentioned before, the tick count since boot time.”]
Source: https://blog.malwarebytes.com/cybercrime/2013/09/in-computers-are-random-numbers-really-random/