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Sparsh Gupta
Asked: 2011-02-26 03:02:42 +0800 CST

CSF log files Interpretation

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I just installed CSF firewall on my server and I have started seeing the following entries in my log file. Can some one help me understanding as to what is happening

Thanks

Feb 25 10:45:19 li235-57 kernel: Firewall: *TCP_IN Blocked* IN=eth0 OUT= MAC=fe:fd:ad:ff:e1:39:88:43:e1:7c:75:3f:08:00 SRC=81.4.153.90 DST=173.255.225.57 LEN=48 TOS=0x00 PREC=0x00 TTL=116 ID=58295 DF PROTO=TCP SPT=43639 DPT=4899 WINDOW=65535 RES=0x00 SYN URGP=0 
Feb 25 10:45:22 li235-57 kernel: Firewall: *TCP_IN Blocked* IN=eth0 OUT= MAC=fe:fd:ad:ff:e1:39:88:43:e1:7c:75:3f:08:00 SRC=81.4.153.90 DST=173.255.225.57 LEN=48 TOS=0x00 PREC=0x00 TTL=116 ID=58483 DF PROTO=TCP SPT=43639 DPT=4899 WINDOW=65535 RES=0x00 SYN URGP=0 
Feb 25 10:55:51 li235-57 kernel: Firewall: *UDP_IN Blocked* IN=eth0 OUT= MAC=fe:fd:ad:ff:e1:39:88:43:e1:7c:75:3f:08:00 SRC=82.178.69.36 DST=173.255.225.57 LEN=50 TOS=0x00 PREC=0x00 TTL=108 ID=3839 DF PROTO=UDP SPT=52904 DPT=80 LEN=30 
Feb 25 10:58:04 li235-57 kernel: Firewall: *UDP_IN Blocked* IN=eth0 OUT= MAC=fe:fd:ad:ff:e1:39:88:43:e1:7c:75:3f:08:00 SRC=82.178.182.44 DST=173.255.225.57 LEN=55 TOS=0x00 PREC=0x00 TTL=47 ID=54421 DF PROTO=UDP SPT=53915 DPT=80 LEN=35
ubuntu networking iptables csf

1 Answers

  1. this means it has blocked the following 3 ip's for the respective reasons

    81.4.153.90 connecting to port 4899 on tcp 82.178.69.36 connecting to port 80 via UDP 82.178.182.44 connecting to port 80 via UDP

    from my knowledge a webserver doesnt run on UDP ports hence why your firewall will block UDP 80

    these are blocked because CSF will generally block IP's that try to connect multiple times to same non open port

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