What is the purpose of malware, viruses, and worms?

Is it just malicious intention to set out and destroy, or do they actually benefit from sending this to your computer.





I've been cleaning up my computer, I installed zonealarm firewall, avast AV, and malwarebytes, and I had a couple trojans and some malware. How do they benefit from putting this on my computer? What do they do with it, do they watch your screens and track you, or is it more of an automatic thing that will take credit card numbers?|||To infect computers duh|||most of it is financial.the hacker gangs that produce the rouge programs make millions of dollars off gullible people.its not like the early days of the net.sure there are hackers that might have a "cause" but at the end of the day the big motive is money.and sad to say it is working very well on windows computers.|||Steal credit card numbers, they could take your passwords to Facebook, Y!A, etc, and sometimes, they just want to destroy your computer.|||worms and such can send out data from your computer, like keyloggers they record everything you type like credit card numbers and usernames/passwords and send them to the creator