The cyber attack that led to operations and appointments being cancelled at NHS Lanarkshire was another "ransomware" case.
The malicious software has been identified as a programme called Bitpaymer, a new type of ransomware which was able to get past existing security measures.
Bitpaymer locks away files and demands payments in Bitcoins, an online currency, to unlock them.
It also threatens to release files if the payment is not received but NHS Lanarkshire said it had no reports this had happened.
Another ransomware program, Wanna Decryptor, affected organisations around the world in May including NHS Lanarkshire.
IT experts discovered Bitpaymer on the computer network on Friday afternoon, with a "small number" of hospital operations and GP appointments cancelled as a result.
All of the affected systems have now been restored, the health board said.
Chief executive Calum Campbell said: "We quickly identified the source of the malware and investigations are ongoing as to how this was able to infiltrate our network.
"Our staff have worked hard to minimise the impact on patients and our contingency plans have ensured we have been able to continue to deliver services while the IT issues were resolved.
"A small number of systems were affected with the majority restored over the weekend and the remainder on Monday."
He continued: "Unfortunately a small number of procedures and appointments were cancelled as a result of the incident.
"I would like to apologise to anyone who has been affected by this disruption. We immediately started work to reappoint patients to the earliest possible appointments.
"The malware was identified as a new variant of Bitpaymer."
He added: "We are investigating how it infiltrated our network with our IT security providers.
"Our security software and systems were up to date with the latest signature files, but as this was a new malware variant the latest security software was unable to detect it.
"Following analysis of the malware our security providers issued an updated signature so that this variant can now be detected and blocked."
NHS Lanarkshire serves a population of more than 650,000 people and is Scotland's third-largest health board.