how can I tell if I have a virus

According to who? A pop up message in your web browser?

Are you sure the phone call came from your bank? Verify it. There are no viruses that attack OS X so I'd be very cautious here.

If your account were compromised, it would also very likely be empty now. I presume your funds are all there?

As macjack said, call your bank and confirm the call came from them. Then ask them what makes them believe it's been compromised.

I'm very sorry to hear that. People tend to call just about any kind of malware a virus. While there are no viruses that can affect a Mac there are known malwares. If you're also running Windows then viruses do become a threat. This sounds more like the work of some kind of keylogger, hacking or physical access to your Mac. Or, it may have been that many of your banks accounts were affected and that the threat is theirs and happened on their systems.

For Mac the only malware detection I'd trust would be MalwareBytes. Malwarebytes was developed by one of our own colleagues here in ASC and is about the most proven anti-malware software for Mac. In any case, I'd follow the advice of your bank and reset all your devices to default, which will ensure there's nothing on your new system that shouldn't be there and copy over only your essential data files, checking again for malware.

rkkbfinn wrote:

I received a call from my bank sharing that it was compromised. I have to scrub all my devices and check for viruses

You have received a stock suggestion from your bank more applicable to Windows users than Mac users, as well as to redirect responsibility for the issue back onto you. There is no known Mac malware that is known to collect bank account information, and no Mac malware currently in distribution contains a keylogger. If someone untrustworthy has had physical access to your machine, they could have installed a keylogger, but unless you have a specific reason to believe otherwise, that's extremely unlikely.

Most likely, anything that Malwarebytes Anti-Malware for Mac finds will not be responsible for this issue. It may be due to a vulnerability in your bank's systems, or could be caused by use of a weak password on your online account with your bank, or could be something else entirely (like someone who has managed to find your checking account number, for example).

If Malwarebytes finds anything and your bank tries to dodge responsibility as a result, be aware that any detection starting with "Adware" or "PUP" is absolutely not responsible for any bank account breaches. Don't let them try to tell you otherwise.

Just an FYI, as you posted in the Mac OS X v10.6 forum, MalwareBytes will not run on your Mac, as it requires a newer OS X version.