"alien technology" can mean technology not related to people of your homeland. So it could mean technology from another country.
From what I heard of McKinnon's exploits, the attack itself exploited a grey area or loophole in how information at the time was being moved from one media to another and undergoing "reclassification". It was posed the exploit involved using the Archie gopher service which contained information stored in this older data format.
As for the US claim that a number of computers were "wiped", there is no third-party confirmation of this, if anything it's just a method to improve the reasons for extradition. However posed exploitation of such computers likely used the "Unmanned Installation" versions of certain operating systems that usually had "Administrator" being created with a "Blank" password, which actually proves a failing in the security protocols that would be assumed to be in place.
As for the information obtained, while UFO secrecy might of been McKinnon's objective, he was technically looking in the wrong place. The Roswell crash of 1947 wasn't investigated directly by the NSA or CIA, but was actually USA-AF with an attempted coup by the FBI head of the time (Hoover) to gain rights over continued investigation.
Any usage of "Alien" by the NSA or the CIA therefore is relationship to "person(s) not being of their country".