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ACL issue & DOS attack

imranraheel
Level 1
Level 1

I have the specified configurations on my 2821 router

interface FastEthernet0/0

ip address 66.x.x.x 255.255.255.248

  ip access-group INBOUND in

  no ip redirects

  ip nbar protocol-discovery

  ip inspect fw out

  speed 100

  full-duplex

  service-policy input FTP-QoS

  service-policy output FTP-QoS

Following is the fw desctiption applied on outbound direction.

  ip inspect name fw dns

  ip inspect name fw tcp

  ip inspect name fw udp

  ip inspect name fw icmp

  ip inspect name fw ftp

  ip inspect name fw http

  ip inspect name fw https

  ip inspect name fw pop3

  ip inspect name fw imap3

  ip inspect name fw ntp

  ip inspect name fw ftps

  ip inspect name fw isakmp

  ip inspect name fw ipsec-msft

  ip inspect name fw l2tp

Inbound ACL Description.

Extended IP access list INBOUND

100 permit tcp any host 66.x.x.x eq 22 log (51 matches)

110 permit tcp any 209.x.x.0 0.0.0.255 eq 10111 log (9089431 matches)

120 permit tcp any 209.x.x.0 0.0.0.255 eq 10112 log

130 permit tcp any 209.x.x.0 0.0.0.255 eq 10113 log (11781 matches)

140 permit tcp any 209.x.x.0 0.0.0.255 eq 10311 log (800041 matches)

150 permit tcp any 209.x.x.0 0.0.0.255 eq 10313 log (1423114 matches)

160 permit tcp any 209.x.x.0 0.0.0.255 eq 10315 log

  170 permit tcp any 209.x.x.0 0.0.0.255 eq 10316 log

  180 permit tcp any 209.x.x.0 0.0.0.255 eq 10321 log (417 matches)

1700 permit tcp any any established log (175963 matches)

  1710 permit icmp any any echo-reply log (1 match)

   1720 deny ip any any log (211516 matches)

I have recently attacked by a DOS attack in which source port was 80 , is there any issues with my configs . As according to the above configs port 80 isnt allowed in .

Can any one please confirm.

Thanks

1 Reply 1

andhingr
Cisco Employee
Cisco Employee

Your FW is inspecting all outgoing http traffic so that return packets are allowed through the acl applied inbound on the interface. The return packets will have the source port of 80 so its possible that if there is man-in-the middle attacks somebody hijacks the initial connection going on destination port 80 and responds with source port of 80.

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