Virus protection

Dear all I am setting a server (running suse linux 7.1) and i will have the following services running: jakarta-tomcat-3.2.3 (html server) postgresql (database) ssh smtp That means ports 8080, 25, 22 and 5342 I believe the system is quite safe like this since im using the latest patches and all. The problem is that the system is lying in a network with quite a few viruses. So i was wondering if instead of installing antivirus software, im better off enabling the suse firewall and giving access only to the specified ports which are needed. Otherwise deny everything else. Will that solve my problem? (will the virus packets be rejected by the firewall). Thanks Marios