Pysa ransomware group has claimed the responsibility for the cyber attack launched last year
The operation appears to be an intelligence gathering effort, rather than an act of cyber warfare, agencies say
But no changes were made to the code, Microsoft asserts
But none of the company's products or services were affected, Cisco says
The spyware exploited an iMessage vulnerability in iOS
But the major target was the US government
CISA has warned about the difficulty of completely ridding the government network of malware
But hackers may still have other means to retain access to victim networks, security experts warn
Update to remove malware planned for release today
No evidence of guest accounts having compromised by hackers but sandwich firm advises anyone who may have downloaded malware to perform a thorough scan of their machine