Q: My keyboard is acting up; typing strange characters, why is that?

Could you post a screen shot, please?

You have been told correctly.  Macs do not get viruses (with exceptions for some malware) but I think we can safely say this is not a virus.

Did you get an answer to your question, irrespective of erroneous symbols?

This discussions thread may give you a clue.   Worth checking the condition of your keyboard and if the ALT key is sticking.   Also try another keyboard to see if that works correctly.

Keyboard typing weird letters and...: Apple Support Communities

Glad to have helped a little.

Who knows as far as the battery is concerned.     Changing it would be good anyway.   But are we discussing two different keyboards here.

If you are using a second board (the one with the low battery) as a test, clearly it needs to be in full working order.

That looks like what might happen if you were typing with the option key pressed. Possibly your keyboard has that key stuck down. It's also possible, if this is a Bluetooth keyboard, that the battery is low, which can cause very strange behavior.

It's entirely possible for a key to be stuck without that being visibly apparent. If replacing the battery doesn't help, you really need to try another keyboard, and/or try that keyboard on another computer.

By the way, is it possible the my computer is hacked? I updated my VLC player and the strange letters started happening.

No. There is no known Mac malware that behaves this way, and there would be no reason for malware to behave that way in the first place. In fact, it would be a really stupid thing to do, since it would prompt people to ask the very question you just did, resulting in a threat to the malware's continued presence.

This is just a keyboard problem of some kind.

So you seem to have two views in agreement.   A virus is not involved and the fault probably lies with your keyboard.

Change the battery, recheck the Alt key functions correctly, then let us know what happened.

Good luck.