I'm not entirely sure if you're asking how to Show, don't Tell, or when to do it, so I'll answer when to do it. (See the end of this answer for links on "Showing, not telling").
You don't have to Show everything. Part of the mastery of writing is to know when to show and when to tell.
Use scene intensity to determine when to show and when to tell
James Scott Bell suggests ranking your scenes for intensity on a 0–10 scale, in his "Revision and Self-Editing for Publication". Anything that falls below 5 should tend towards telling rather than showing and anything that falls above 5 should tend towards showing rather than telling.
(And anything that gets an intensity of 0 should be rewritten or cut...)
In essence, this means you'll spend fewer words on low-intensity scenes (telling is usually going to result in fewer words for doing the same thing) and more words on high-intensity scenes (since showing generally use more words).
Exactly what the reader wants. Lots of high-intensity scenes interspersed with vital low-intensity telling.
Use Scenes and Sequels
Dwight Swain in "Techniques of the Selling Writer" introduces Scenes and Sequels.
The Sequel will contain more telling, it's short and jam-packed with information such as backstory and flashbacks, deliberation on how to solve the problem of the previous disastrous scene, even small non-dramatic scenes called incidents and gatherings where things do indeed go as planned.
The main purpose of the Sequel is to propel the reader from one Scene (action you show, don't tell) to the other with as few words as we can get away with.
So telling is good for dull transportation or non-dramatic but vital passages. Stuff that maybe could be made dramatic but doing so doesn't contribute to the story actually being told.
Should you show or tell the virus installation?
In the case of the virus installation, I think it's a question of in whose perspective the text is written. If it's the hacker's perspective I'd say go with telling, likely they install a thousand viruses every day, and some even joke the ransomware gangs' customer support is better than any internet provider's because they can even teach grandmas how to buy and transfer bitcoins. For the hacker, it's likely another day at the "office." Low intensity.
If on the other hand, this is from the victim's perspective, then showing the actual effects of the virus is likely better, especially since it is likely to be emotional and dramatic to the character. It will be a high-intensity scene.
How to Show, not Tell on Writing.SE
If you want to know how to "Show, don't Tell" Writing.SE contains many examples: