fragrouter - network intrusion detection evasion toolkit

fragrouter [ -i interface ] [ -p ] [ -g hop ] [ -G hopcount ] ATTACK

Fragrouter is a program for routing network traffic in such a way as to elude most network intrusion detection systems.

Most attacks implemented correspond to those listed in the Secure Networks ``Insertion, Evasion, and Denial of Service: Eluding Network Intrusion Detection'' paper of January 1998.

-i

Specify the interface to accept packets on.

-p

Preserve the entire protocol header in the first fragment. This is useful in bypassing packet filters that deny short IP fragments.

-g

Specify a hop along a loose source routed path. Can be used more than once to build a chain of hop points.

-G

Positions the "hop counter" within the list of hosts in the path of a source routed packet. Should be a multiple of 4. Can be set past the length of the loose source routed path to implement Anthony Osborne's Windows IP source routing attack of September 1999.

The following attack options are mutually exclusive - you may only specify one type of attack to run at a time.

-B1

baseline-1: Normal IP forwarding.

-F1

frag-1: Send data in ordered 8-byte IP fragments.

-F2

frag-2: Send data in ordered 24-byte IP fragments.

-F3

frag-3: Send data in ordered 8-byte IP fragments, with one fragment sent out of order.

-F4

frag-4: Send data in ordered 8-byte IP fragments, duplicating the penultimate fragment in each packet.

-F5

frag-5: Send data in out of order 8-byte IP fragments, duplicating the penultimate fragment in each packet.

-F6

frag-6: Send data in ordered 8-byte IP fragments, sending the marked last fragment first.

-F7

frag-7: Send data in ordered 16-byte IP fragments, preceding each fragment with an 8-byte null data fragment that overlaps the latter half of it. This amounts to the forward-overlapping 16-byte fragment rewriting the null data back to the real attack.

-T1

tcp-1: Complete TCP handshake, send fake FIN and RST (with bad checksums) before sending data in ordered 1-byte segments.

-T3

tcp-3: Complete TCP handshake, send data in ordered 1-byte segments, duplicating the penultimate segment of each original TCP packet.

-T4

tcp-4: Complete TCP handshake, send data in ordered 1-byte segments, sending an additional 1-byte segment which overlaps the penultimate segment of each original TCP packet with a null data payload.

-T5

tcp-5: Complete TCP handshake, send data in ordered 2-byte segments, preceding each segment with a 1-byte null data segment that overlaps the latter half of it. This amounts to the forward-overlapping 2-byte segment rewriting the null data back to the real attack.

-T7

tcp-7: Complete TCP handshake, send data in ordered 1-byte segments interleaved with 1-byte null segments for the same connection but with drastically different sequence numbers.

-T8

tcp-8: Complete TCP handshake, send data in ordered 1-byte segments with one segment sent out of order.

-T9

tcp-9: Complete TCP handshake, send data in out of order 1-byte segments.

-C2

tcbc-2: Complete TCP handshake, send data in ordered 1-byte segments interleaved with SYN packets for the same connection parameters.

-C3

tcbc-3: Do not complete TCP handshake, but send null data in ordered 1-byte segments as if one had occured. Then, complete a TCP handshake with same connection parameters, and send the real data in ordered 1-byte segments.

-R1

tcbt-1: Complete TCP handshake, shut connection down with a RST, re-connect with drastically different sequence numbers and send data in ordered 1-byte segments.

-I2

ins-2: Complete TCP handshake, send data in ordered 1-byte segments but with bad TCP checksums.

-I3

ins-3: Complete TCP handshake, send data in ordered 1-byte segments but with no ACK flag set.

-M1

misc-1: Thomas Lopatic's Windows NT 4 SP2 IP fragmentation attack of July 1997 (see http://www.dataprotect.com/ntfrag/ for details). This attack has only been implemented for UDP.

-M2

misc-2: John McDonald's Linux IP chains IP fragmentation attack of July 1998 (see http://www.dataprotect.com/ipchains/ for details). This attack has only been implement for TCP and UDP.

tcpdump(8), tcpreplay(8), pcap(3), libnet(3)

Dug Song, Anzen Computing.

The current version is available via HTTP:

http://www.anzen.com/research/nidsbench/

IP options will carry across all fragments of a packet. Fragrouter is not smart enough to determine which IP options are valid only in the first fragment. This is considered a feature, not a bug. :-)

Similarly, TCP options will carry across all segments of a split TCP packet - except for null data packets preceding a forward overwrite, which lack any TCP options in order to elude TCP PAWS elimination.

Please send bug reports to nidsbench@anzen.com.