"The attack vector has all the hallmarks of a traditional computer worm," CrowdStrike vice president of intelligence Adam Meyers told ARN.
"We've not seen a large-scale ransomware campaign that uses self-propagating technique at this scale before, which makes it really unique."
Meyers said targeting was likely in bulk, via massive phishing campaigns delivering .zip archives with themes such as fake invoices, job offers, security warnings, undelivered email.
"Once an infection takes place, Wana encrypts victim files using the AES-128 cipher, and demands a Bitcoin ransom of increasing value as time passes," Meyers explained.
"Files encrypted by Wana are appended with a file extension of .wncry. Observed ransom demands require victims to pay either US$300 or US$600 worth of Bitcoin for a decryption key."
According to Meyers, early analysis of the worm is that it is taking advantage of a very recent Microsoft Windows exploit called EternalBlue, which is the enabler for how files get shared.
"Swift action to patch against this update is critical," Meyers added. "Whilst ensuring that back-up data files are disconnected from the core network, as this ransomware has the potential to encrypt back-up files."
Early reports show the malware originating in Europe and impacting healthcare organisations, hospitals, surgeries, telecommunication systems as well as gas and electricity utilities.
"The group behind the attack does not appear to be picky about the nation or sector it is targeting," Meyers added.
This is what the victim's wallpaper is changed to following the breach. Credit: Avast Software
After WannaCry encrypts data files and asks users to pay a US$300 ransom in Bitcoins, the ransom note indicates that the payment amount will be doubled after three days.
If payment is not made after seven days, the encrypted files will be deleted.
"WannaCry has the ability to spread itself within corporate networks, without user interaction, by exploiting a known vulnerability in Microsoft Windows," a Symantec Security Response statement read.
"Computers which do not have the latest Windows security updates applied are at risk of infection."
While the breaches appear to be linked, researchers believe it may not be a coordinated attack on specific targets, a theory backed up by UK Prime Minister Theresa May.
"This is not targeted at the NHS, it's an international attack and a number of countries and organisations have been affected," May said on 12 May.
Increased activity of the ransomware strain was first globally reported at 8am Central European Time (CET) on 12 May, with attacks then rapidly increasing across the world during the next 24 hours.
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