WinPcap过滤表达式知识

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CaptureFilters
An overview of the capture filter syntax can be found in the User's Guide. A complete reference can be found in the expression section of the tcpdump manual page.

Wireshark uses the same syntax for capture filters as tcpdump, WinDump, Analyzer, and any other program that uses the libpcap/WinPcap library.

If you need a capture filter for a specific protocol, have a look for it at the ProtocolReference.

Contents

1. CaptureFilters

1. Examples

2. Useful Filters

3. Default Capture Filters

4. Further Information

5. See Also

6. Discussion

Examples
Capture only traffic to or from IP address 172.18.5.4

· host 172.18.5.4
Capture traffic to or from a range of IP addresses:

· net 192.168.0.0/24
or

· net 192.168.0.0 mask 255.255.255.0
Capture traffic from a range of IP addresses:

· src net 192.168.0.0/24
or

· src net 192.168.0.0 mask 255.255.255.0
Capture traffic to a range of IP addresses:

· dst net 192.168.0.0/24
or

· dst net 192.168.0.0 mask 255.255.255.0
Capture only DNS (port 53) traffic:

· port 53
Capture non-HTTP and non-SMTP traffic on your server (both are equivalent):

· host https://www.sodocs.net/doc/4c8908732.html, and not (port 80 or port 25)
host https://www.sodocs.net/doc/4c8908732.html, and not port 80 and not port 25
Capture except all ARP and DNS traffic:

· port not 53 and not arp
Capture traffic within a range of ports

· (tcp[0:2] > 1500 and tcp[0:2] < 1550) or (tcp[2:2] > 1500 and tcp[2:2] < 1550)
or, with newer versions of libpcap (0.9.1 and later):

· tcp portrange 1501-1549
Capture only Ethernet type EAPOL:

· ether proto 0x888e
Reject ethernet frames towards the Link Layer Discovery Protocol Multicast group:

· not ether dst 01:80:c2:00:00:0e
Capture only IP traffic - the shortest filter, but sometimes very useful to get rid of lower layer protocols like ARP and STP:

· ip
Capture only unicast traffic - useful to get rid of noise on the network if you only want to see traffic to and from your machine, not, for example, broadcast and multicast announcements:

· not broadcast and not multicast
Capture HTTP GET requests. This looks for the bytes 'G', 'E', 'T', and ' ' (hex values 47, 45, 54, and 20) just after the TCP header. "tcp[12:1] & 0xf0) >> 2" figures out the TCP header length. From Jefferson Ogata via the tcpdump-workers mailing list.

· port 80 and tcp[((tcp[12:1] & 0xf0) >> 2):4] = 0x47455420
Useful Filters
Blaster and Welchia are RPC worms. (Does anyone have better links, i.e. on

es that describe or show the actual payload?)

Blaster worm:

· dst port 135 and tcp port 135 and ip[2:2]==48
Welchia worm:

· icmp[icmptype]==icmp-echo and ip[2:2]==92 and icmp[8:4]==0xAAAAAAAA
The filter looks for an icmp echo request that is 92 bytes long and has an icmp payload that begins with 4 bytes of A's (hex). It is the signature of the welchia worm just before it tries to compromise a system.

Many worms try to spread by contacting other hosts on ports 135, 445, or 1433. This filter is independent of the specific worm instead it looks for SYN packets originating from a local network on those specific ports. Please change the network filter to reflect your own network.

dst port 135 or dst port 445 or dst port 1433 and tcp[tcpflags] & (tcp-syn) != 0 and tcp[tcpflags] & (tcp-ack) = 0 and src net 192.168.0.0/24
Default Capture Filters
Wireshark tries to determine if it's running remotely (e.g. via SSH or Remote Desktop), and if so sets a default capture filter that should block out the remote session traffic. It does this by checking environment variables in the following order:


Environment Variable
Resultant Filter

SSH_CONNECTION
not (tcp port srcport and addr_family host srchost and tcp port dstport and addr_family host dsthost)

SSH_CLIENT
not (tcp port srcport and addr_family host srchost and tcp port dstport)

REMOTEHOST
not addr_family host host

DISPLAY
not addr_family host host

CLIENTNAME
not tcp port 3389


(addr_family will either be "ip" or "ip6")

Further Information
Filtering while capturing from the Wireshark User's Guide
The tcpdump man page includes a comprehensive capture filter reference
The Mike Horn Tutorial gives a good introduction to capture filters
Capture and display filter Cheat sheets
packetlevel.ch Filter examples
See Also
DisplayFilters: more info on filters while displaying, not while capturing

The String-Matching Capture Filter Generator

Discussion
BTW, the Symantec page says that Blaster probes 135/tcp, 4444/tcp, and 69/udp. Would

· (tcp dst port 135 or tcp dst port 4444 or udp dst port 69) and ip[2:2]==48
be a better filter? - Gerald Combs
Q: What is a good filter for just capturing SIP and RTP packets?

A: On most systems, for SIP traffic to the standard SIP port 5060,

· tcp port sip
should capture TCP traffic to and from that port,

· udp port sip
should capture UDP traffic to and from that port, and

· port sip
should capture both TCP and UDP traffic to and from that port (if one of those filters gets "parse error", try using 5060 instead of sip). For SIP traffic to and from other ports, use that port number rather than sip.

In most cases RTP port numbers are dynamically assigned. You can use something like the following which limits the capture to UDP, even source and destination ports, a valid RTP version, and small packets. I

t will capture any non-RTP traffic that happens to match the filter (such as DNS) but it will capture all RTP packets in many environments.

· udp[1] & 1 != 1 && udp[3] & 1 != 1 && udp[8] & 0x80 == 0x80 && length < 250
Capture WLAN traffic without Beacons:

· link[0] != 0x80
Capture all traffic originating (source) in the IP range 192.168.XXX.XXX:

· src net 192.168
Capture PPPoE traffic:

· pppoes
· pppoes and (host 192.168.0.0 and port 80)
Capture VLAN traffic:

· vlan
· vlan and (host 192.168.0.0 and port 80)

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CategoryHowTo
CaptureFilters (last edited 2011-04-26 14:05:16 by VitalyKuznetsov)

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