more info on mac antivirus re ddos wpress attack, please

i understand the ddos attack(s) issues have to be resolved for each of us by contacting our host, but i am told it was hugely on wordpress sites, so would like to talk with others here. i use a mac, wp 3.4.2 and run a news site (lewis county sirens.com) and my host blacklisted my ip address this morning, until i use some antivirus to clean whatever off my computer. i’ve NEVER gotten a virus on my mac. my host (bluehost) suggested i use “avast” free anti virus software for macs. anyone agree? disagree? is there going to be something else i should do? thanks in advance. –s