One victim who was tracked down by the company confessed that he/she had not bothered to even set a password for the server in question.
The company said it had named the ransomware QNAPCrypt as this appeared to be the name given to it by the authors. QNAP sells NAS servers.
Intezer's Ignacio Sanmillan said the detection rate of the ransomware was quite low, adding that there were both ARM and x86 variants.
A message from a user whose NAS server was infected, indicating the laxity in password policy. Courtesy Intezer
Additionally, once a server was compromised, QNAPCrypt sought a wallet address and a public RSA key from its command and control server before encrypting files.
Sanmillan said Intezer simulated a denial of service attack on the infrastructure used by the malware.
"After simulating the infections of hundreds of virtual 'victims', we discovered two major design flaws in the ransomware infrastructure which led us to seize the operation," he wrote.
One was that the list of bitcoin wallets was created in advance and it was static. "Therefore, it does not create a new wallet for each new victim in real time, but rather it pulls a wallet address from a fixed, pre-determined list."
The second characteristic was that once all the wallets were allocated (or sent), the ransomware would not be able to continue its malicious operation on the victim’s machine.
After simulating the infection of more than 1091 victims, Sanmillan said the number of bitcoin wallet addresses ran out. "As a result, any future infection will be unsuccessful and the authors behind this malware were forced to update their implants in order to circumvent this design flaw in their infrastructure to continue with their malicious operations," he wrote.