Malicious software developers want their products to meet a lot of the same requirements that other software should meet. It's not desirable, for example, for either type of program to crash user computers or applications.
In the case of regular software, causing crashes indicates that the software is not functional. If malware crashes user systems, on the other hand, the larger concern is that the cause of the crash will be detected, eradicated and reported. Running smoothly without causing problems is generally the ideal for malware as much as it is for any software because anything that causes problems is likely to be investigated.
Brandon Dixon, an independent researcher, reported that two high-profile nation state hacking teams were using Google's VirusTotal website to improve their malware. VirusTotal is a free service that allows any user to submit a program for testing. The site aggregates over three dozen antivirus scanners from Symantec, Kaspersky Lab, F-Secure and others. Dixon had been tracking submissions to the site for some time.
To test their malware, the hacking teams repeatedly submitted programs to the site attempting to ensure they can evade detection by antivirus software. When a program failed to get through antivirus, they would tweak the code and resubmit until the malware was able to pass undetected.