FRAGROUTER(8)FRAGROUTER(8)NAMEfragrouter - network intrusion detection evasion toolkit
SYNOPSISfragrouter [ -i interface ] [ -p ] [ -g hop ] [ -G hopcount ] ATTACK
DESCRIPTION
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 Net‐
works ``Insertion, Evasion, and Denial of Service: Eluding Network
Intrusion Detection'' paper of January 1998.
OPTIONS-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 frag‐
ments.
-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 frag‐
ment 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, duplicat‐
ing 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 seg‐
ments, duplicating the penultimate segment of each original TCP
packet.
-T4 tcp-4: Complete TCP handshake, send data in ordered 1-byte seg‐
ments, 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 seg‐
ments, preceding each segment with a 1-byte null data segment
that overlaps the latter half of it. This amounts to the for‐
ward-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 seg‐
ments interleaved with 1-byte null segments for the same connec‐
tion but with drastically different sequence numbers.
-T8 tcp-8: Complete TCP handshake, send data in ordered 1-byte seg‐
ments 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 seg‐
ments 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 seg‐
ments but with bad TCP checksums.
-I3 ins-3: Complete TCP handshake, send data in ordered 1-byte seg‐
ments 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.
SEE ALSOtcpdump(8), tcpreplay(8), pcap(3), libnet(3)AUTHOR
Dug Song, Anzen Computing.
The current version is available via HTTP:
http://www.anzen.com/research/nidsbench/
BUGS
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.
26 April 1999 FRAGROUTER(8)
