I find that virus disinfect missions are just weird...
A few things I have found:
1) Virus disinfect missions give good cash - so good in fact people spend time installing viruses... and then killing their own virii!!!
2) Trying to install a virus as a newbie on a public server is a very very frustrating waste of time. I know that there is a small chance there will be no mission generated, but it takes a lot of your meager resources to get a virus up and running... and often it's killed within hours. (Ok not if it's a file share virus, but those take even longer to do anything)
3) Virii installed by the stronger players are kept in place by the threat of retaliation from the stronger players.
Ok so here is my suggestion:
Have the rewards for virii disinfect missions scale up with time.
Literally they should be small to start with, but the longer a virus runs on a given machine, the higher the reward would go up.
Possible scenarios - run checks every 6 hours a virus is running (maybe have different times for different virii) say give it a 50% chance for the reward to go up. Start with a base reward which is maybe 20% of the current reward. As time passes the reward becomes more and more important... to the point when someone will attempt the disinfect mission even against the big virii out there (though for the sake of balance a cap should be placed on the reward offered maybe)
This could work in one of two ways: 1) A new mission is generated. Thus there are several missions available for each virus (cumulative returns) or 2) The value of existing missions is increased. The question with the second option is how much does someone get paid - the value of the mission when they accepted the mission or the value of the mission when they completed the mission? (The second case is somewhat open to abuse when someone completes a mission but does "not" press "complete" while waiting for the value of the mission to increase)...
Ok just some ideas from a younger player