The Wireshark Display Filter Reference page lists all display filters and which versions of Wireshark each display filter applies to.If you don't know the name of the display filter, you can look it up at least 3 differnet ways: You can also add columns via the main menu, but if you add them this way, you'll have to know the Wireshark display filter name in order to type it in when adding it, which you can do by: Edit -> Preferences -> Columns -> + ->. Once added, you can drag and drop the field to any desired column location. Now, if you right-click on the field, you can choose Apply as Column. This is one way to learn the display filter for a given field. When you select it, you'll notice the status line at the bottom of the Wireshark window will show you what the Wireshark display filter is for that field, and in this example, it'll be modbus.func_code. #pcap filter expr " port 80 and (tcp & 0xf0) > 2):4] = 0x47455420 or tcp & 0xf0) > 2)+8:4] = 0x20323030)"Īlternatively, in the UI go to Maintenance > Service Information > Packet Captures and enter just the filter you want into the filter section (quotation marks are not needed).For each field you want to add as a column, the easiest way is to first select the field, let's say the "Function Code" as an example. To use this on a ProxySG, either enter the command line entry as follows (take note to use quotation marks):
You can also add things like DNS by adding another port: You could specify "304" or "500" by determining what the hex values for those items is. Instead of "GET " you could use the hex values for "HEAD" or "POST".
The values can be changed by replacing with the data you want. By using the filter above, you can gather only GETs with valid, new content responses. This filter is very powerful on a very busy ProxySG, as sometimes there is enough data traversing the proxy to only capture a few seconds before hitting the 100 MB limit. A typical HTTP response will start with "HTTP/1.1 200 OK".
The third bullet is offset by 8 bytes and is for an HTTP response. The second bullet restated says "TCP offset 47455420" which is literally "GET " (G, E, T, space) Most common for a transparent HTTP environment. The first part is to only capture TCP or UDP port 80. The following information is taken in part from the Wireshark Wiki page on capturing HTTP GET requests ( /CaptureFilters).
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