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Speed of computer virus infection

A computer is infected with the Sasser virus. Assume that it infects 20 other computers within 5 minutes; and that these PCs and servers each infect 20 more machines within another five minutes, etc. How long until 100 million computers are infected?

Solution Preview

Hello and thank you for posting your question to Brainmass.

There are two ways to look at the problem. Each way leads to a different solution. I suspect you are looking for the firs solution. However I thought it would be useful to show you both.

Solution #1 - The discrete propagation:

We asume that the infection is done in time steps. That is at t=0 there is one infected machine, and only at t=5 we have additional 20 infected machines.

Let n be the 5 minutes step (t=5n).

After 5 minutes (n=1) we have 20+1 computers infected.

Then, after another 5 minutes (n=2) each of these computers infect 20 more, so together we have the (20+1) originals plus 20*(20+1) new ...

Solution Summary

The solution shows how to estimate the infection rate of computers by a virus if the infection is done in (a) discrete steps or (b) continuous spread.

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