galaxy s2 cellphone problem; possible virus I read that it is used on the computer. 

It has been coming up on my Android Galaxy 2 s. It is on at least 3 times at once and up to 7 or 8 at once. They are called kworker/0:1 through kworker/0:4 and/or kworker/u:1 through kworker/u:4 

Occasionally, it comes up as using about 80 % of the CPU. My phone also regularly crashes as of recently. Could kworker be the problem? 

The virus I have also is kind of trojan-based and has popups when I restart my phone sometimes. Also, when my phone is asleep, and i turn it back on, it says kworker is using 100% of my CPU data.
Uhhhh, that is not a virus! Who told you that? :)

kworker is part of the Linux Kernel's scheduler in which it manages the processes running and switching to it a la multitasking. 

That is normal behaviour of the kernel! It exists on the desktop linux also, see this example to illustrate:

ps -elf | grep kworker
1 S root         5     2  0  60 -20 -     0 worker Jan31 ?        00:00:00 [kworker/0:0H]
1 S root         6     2  0  80   0 -     0 worker Jan31 ?        00:00:23 [kworker/u:0]
1 S root         7     2  0  60 -20 -     0 worker Jan31 ?        00:00:00 [kworker/u:0H]
1 S root        16     2  0  80   0 -     0 worker Jan31 ?        00:00:16 [kworker/1:0]
1 S root        17     2  0  60 -20 -     0 worker Jan31 ?        00:00:00 [kworker/1:0H]
1 S root        22     2  0  60 -20 -     0 worker Jan31 ?        00:00:00 [kworker/2:0H]


The reason that it is "using about 80 % of the CPU" is that there's some apps running that are consuming a lot of CPU cycles.

All in all, nothing to worry about.