Screenshot of the ransom note left on an infected system
||12 May 2017 – 15 May 2017
|Also known as
Wanna → Wana
Cryptor → Crypt0r
Cryptor → Decryptor
Cryptor → Crypt → Cry
Addition of "2.0"
Wanna → WN → W
Cry → CRY
Ransomware encrypting files with $300 – $600 demand (via
||Over 200,000 victims and more than 300,000 computers infected
The WannaCry ransomware attack was a May 2017
cyberattack by the WannaCry
cryptoworm, which targeted computers running the
operating system by encrypting data and demanding ransom payments in the
The attack began on Friday, 12 May 2017,
 and within a day was reported to have infected more than 230,000 computers in over 150 countries.
 Parts of the United Kingdom's
National Health Service (NHS) were infected, causing it to run some services on an emergency-only basis during the attack
Deutsche Bahn were hit, along with many other countries and companies worldwide.
 Shortly after the attack began,
Marcus Hutchins, a 22-year-old web security researcher from North Devon in England then known as
 discovered an effective
kill switch by registering a
domain name he found in the code of the ransomware. This greatly slowed the spread of the infection, effectively halting the initial outbreak on Monday, 15 May 2017, but new versions have since been detected that lack the kill switch.
 Researchers have also found ways to recover data from infected machines under some circumstances.
WannaCry propagates using
exploit of Windows'
Server Message Block (SMB) protocol. Much of the attention and comment around the event was occasioned by the fact that the U.S.
National Security Agency (NSA) had already discovered the vulnerability, but used it to create an exploit for its own
offensive work, rather than report it to Microsoft.
 Microsoft eventually discovered the vulnerability, and on
Tuesday, March 14, 2017, they issued security bulletin MS17-010, which detailed the flaw and announced that
patches had been released for all Windows versions that were currently supported at that time, these being
Windows Server 2008,
Windows Server 2012, and
Windows Server 2016, in addition to
Windows Vista (which had recently ended support).
 However, many Windows users had not installed the patches when, two months later on May 12, 2017, WannaCry used the EternalBlue vulnerability to spread itself. The next day, Microsoft released emergency security patches for
Windows 7 and
Those still running older,
unsupported versions of
Microsoft Windows, such as
Windows XP and
Windows Server 2003, were initially at particular risk, but Microsoft released an emergency security patch for these platforms as well.
 Almost all victims of the cyberattack were running
Windows 7, prompting a security researcher to argue that its effects on Windows XP users were "insignificant" in comparison.
Within four days of the initial outbreak, security experts said that most organizations had applied updates, and that new infections had slowed to a trickle.
Several organizations released detailed technical writeups of the malware, including Microsoft,
The "payload" works in the same fashion as most modern ransomware: it finds and encrypts a range of data files, then displays a "ransom note" informing the user and demanding a payment in
 It is considered a network worm because it also includes a "transport" mechanism to automatically spread itself. This transport code scans for vulnerable systems, then uses the EternalBlue exploit to gain access, and the
DoublePulsar tool to install and execute a copy of itself.