TCP RST on TELNET - Packet builder

Question

I'm having some troubles building my TCP RST packet. I've a LAN with 3 pc's connected, the host, victim and the attacker.
Im trying to break up the connection that exists between my Host and my Victim over a TELNET connection, using my Attacker to send an TCP RST packet with the NetWag software. I know the source and destination port numbers and ip's but when i send the packet, with Wireshark i can see that it was received by de Victim, but the connection doesn't go down.

Does the problem is in the Sequence and/or Ack numbers?

P.s. both firewalls are shut down.

Answer 1

Yes, the sequence numbers are very important. Packets out of sequence essentially are ignored. In fact, the sequence number used to start at 1 and increment from there but that was later changed to start with a random number to help prevent the very thing you are trying to do.

NOTE: you also have to ensure that the packets are correctly formatted such as having a correct checksum otherwise they will be ignored anyway.