Win32.Sality virus is spreading or spreads?

The Win32.Sality virus disables antivirus and is spreading fast.

Why not ‘is disabling’ and ‘spreads’?

Why ‘The’ is used?

You’re referring to a specific virus, so “the” is used.

“Is spreading” means this is happening now, whereas “spreads” would refer to the general nature of the virus. We could say that it spreads fast even when it’s not in the act of during so.

The flu spreads fast. - A general truth
The flu is spreading fast. - An action in progress

This is the general nature of the simple present and present progressive.

I guess the speaker was more interested in describing the nature of the virus rather than what it was doing at the time when “disables” was chosen.