This isn't a good week for me. First, my Lenovo K 900 gets assaulted by some weird form of sms alerts. Now, my iMac has gone nuts

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Here are my specs. 21.5' iMac, i5, 2.7 GHz, 8 GB RAM and 1 TB HDD.
Was fine until about 30 minutes ago. Now, it is just showing me beachballs, for everything! I mean, I am seeing that stupid beach ball even when I open a browser window! Everything is taking foreveerrr.
I didn't do anything out of the oridinary. Was just chatting on skype. Btw, I have restarted many times but it is just bad every time?
Is this is a malware attack? So weird. Any help is welcome please!