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Graphics Interchange Format  |  1998-02-10  |  39KB  |  429x257  |  4-bit (16 colors)
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OCR: PACKET FILTER Firewall Server X Rejected OK X x Rejected OK X X Figure 3 : A packet filter firewall operates at the lowest level, It checks each packet it receives and forwards only those that are valid. Filtering is based upon packet contents such as the source of destination address.