Network Device System Image Modified via TFTP

Darshan Thummar@Mighty

•updated Jun 11, 2026•0•0•2

This rule detects potential modification of a network device's system image via TFTP. It specifically looks for UDP traffic on port 69 (TFTP) where the packet size is greater than 50000 bytes and contains the byte sequence "|00 02|" at a depth of 2 bytes, which is indicative of a TFTP write request (opcode 2). The large packet size suggests a system image transfer.