Abstract: A data processing system comprising a plurality of computers interconnected through a local network, preferably in the form of a ring. The network being connected to a network adapter which is able to receive all information on the network. The network adaptor is connected to a computer which together with the adaptor can perform an assembling and scanning of substantially all files on the network and carry out a recognition of virus signatures. The individual file packets circulation in the network are assembled, said file packets being assembled in a file and scanned for virus signatures. When a virus signature is detected in the file, information is simultaneously provided on the transmitting stations and the receiving stations, whereafter it is possible to transmit the vaccine to the stations in question.