How do you block empty user-agents?

This is the iRule:

if { [HTTP::header exists "User-Agent"]} { if { [HTTP::header "User-Agent"] equals "" } { reject } }

iRule looks to be good. Try it out. Make sure to add "when HTTP_REQUEST" as the event.

I am getting the following error:

The requested object name (user agents) is invalid

Remove the quotes around User-Agent

I changed it to the following below, but still have the same error.

when HTTP_RESPONSE { if { [HTTP::header exists User-Agent]} { if { [HTTP::header User-Agent] equals "" } { reject } }

If you need to block incoming request from client, you need to use HTTP_REQUEST

I was not able to test these, but either should get you the results you are looking for:

when HTTP_REQUEST { 
if {[class match [HTTP::header "User-Agent"] equals ""]} {
  reject  
}}

OR

when HTTP_REQUEST {
if { [HTTP::header exists User-Agent]} { if { [HTTP::header User-Agent] equals "" } {
    reject
}}}

Good Luck!