Description: Attackers can use specially crafted Read FIFO Queue Request messages to cause a denial of service attacks and to identify weaknesses in the MODBUS/TCP implementation.Notes:This signature checks Modbus Read FIFO Queue function (code: 0x18) request packet against the protocol specification and alerts if the packet does not comply with the protocol.Signature checks the protocol bytes to confirm this is a modbus packet. Length in the protocol for this packet must be 0x04. This is also checked as part of decision to confirm this is modbus packet. If this value or protocol bytes are not correct, then the packet is considered as non modbus traffic and no alert is generated.Then, packet size is checked to confirm no trailing data exceeding the expected size of 4 bytes. False Negatives:Short packets will not be captured by this signature. Short packets will be captured under it's own signature.False Positives:No known false positives.You are entitled to use this signature only if you have purchased an IPS SCADA Signature License
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