system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU Age of Ultron] How can we be sure Ultron was wiped completely from the Internet?

They say Ultron had infiltrated virtually the entire internet, and then Vision scoured him from it, but, what if there was a computer, say, a supercomputer associated with a college or something, that had Ultron, but was temporarily disconnected from the Internet (weather, ISP outage, shut down for physicalmechanical maintenance up upgrade) that **was not online** during the timeframe when Vision did his scour.

Would it them be possible for that copy of Ultron to hide and bide his time once the Internet is reconnected and he learns that the Avengers defeated him?

Could he come back? Especially with Tony and Vision dead and unable to fight him?
gpt
I imagine Vision left part of himself in the net so he could overpower any Ultron programs that popped up, probably even "vaccinated" the major internet hubs to scrub any Ultron program that tried to pass through them.