If you want to stop (some of the) known viruses that always come in through the same port, add some rules to your Mikrotik firewall.
Paste this into Mikrotik terminal
/ip firewall filter add chain=virus protocol=tcp dst-port=135-139 action=drop comment="Drop Blaster Worm" add chain=virus protocol=udp dst-port=135-139 action=drop comment="Drop Messenger Worm" add chain=virus protocol=tcp dst-port=445 action=drop comment="Drop Blaster Worm" add chain=virus protocol=udp dst-port=445 action=drop comment="Drop Blaster Worm" add chain=virus protocol=tcp dst-port=593 action=drop comment="________" add chain=virus protocol=tcp dst-port=1024-1030 action=drop comment="________" add chain=virus protocol=tcp dst-port=1080 action=drop comment="Drop MyDoom" add chain=virus protocol=tcp dst-port=1214 action=drop comment="________" add chain=virus protocol=tcp dst-port=1363 action=drop comment="ndm requester" add chain=virus protocol=tcp dst-port=1364 action=drop comment="ndm server" add chain=virus protocol=tcp dst-port=1368 action=drop comment="screen cast" add chain=virus protocol=tcp dst-port=1373 action=drop comment="hromgrafx" add chain=virus protocol=tcp dst-port=1377 action=drop comment="cichlid" add chain=virus protocol=tcp dst-port=1433-1434 action=drop comment="Worm" add chain=virus protocol=tcp dst-port=2745 action=drop comment="Bagle Virus" add chain=virus protocol=tcp dst-port=2283 action=drop comment="Drop Dumaru.Y" add chain=virus protocol=tcp dst-port=2535 action=drop comment="Drop Beagle" add chain=virus protocol=tcp dst-port=2745 action=drop comment="Drop Beagle.C-K" add chain=virus protocol=tcp dst-port=3127-3128 action=drop comment="Drop MyDoom" add chain=virus protocol=tcp dst-port=3410 action=drop comment="Drop Backdoor OptixPro" add chain=virus protocol=tcp dst-port=4444 action=drop comment="Worm" add chain=virus protocol=udp dst-port=4444 action=drop comment="Worm" add chain=virus protocol=tcp dst-port=5554 action=drop comment="Drop Sasser" add chain=virus protocol=tcp dst-port=8866 action=drop comment="Drop Beagle.B" add chain=virus protocol=tcp dst-port=9898 action=drop comment="Drop Dabber.A-B" add chain=virus protocol=tcp dst-port=10000 action=drop comment="Drop Dumaru.Y" add chain=virus protocol=tcp dst-port=10080 action=drop comment="Drop MyDoom.B" add chain=virus protocol=tcp dst-port=12345 action=drop comment="Drop NetBus" add chain=virus protocol=tcp dst-port=17300 action=drop comment="Drop Kuang2" add chain=virus protocol=tcp dst-port=27374 action=drop comment="Drop SubSeven" add chain=virus protocol=tcp dst-port=65506 action=drop comment="Drop PhatBot, Agobot, Gaobot" add chain=forward action=jump jump-target=virus comment="jump to the virus chain"