F5 is upgrading its customer support chat feature on My.F5.com. Chat support will be unavailable from 6am-10am PST on 1/20/26. Refer to K000159584 for details.

Forum Discussion

Company_B_88989's avatar
Company_B_88989
Icon for Nimbostratus rankNimbostratus
Mar 02, 2017

ASM: How to block a user holding down F5 Key

A user holding down the F5 key causes constant refreshes and creates too much traffic in our backend. We have the ASM Module and have tried different DOS profile settings, specifically TPS-based and...
ASM Advanced WAF
security
Jason0_309417's avatar
Jason0_309417
Icon for Cirrus rankCirrus
Mar 02, 2017

What TPS limits have you tried? You can always put an iRule in place while you workout the ASM policy. Something to display an error message or do an HTTP::close. 

when HTTP_REQUEST {

    if {[info exists refresh_count] } {

        if { [HTTP::header value "If-Modified-Since"] ne ""  } {
            incr refresh_count
        }

        if { $refresh_count > 10 } {
            HTTP::respond 200 content "Nope"
        }

    } else {
        set refresh_count 0
    }

}
Company_B_88989's avatar
Company_B_88989
Icon for Nimbostratus rankNimbostratus
Mar 02, 2017

Thanks, I am going to try the iRule.

 

The holding down F5 key doesn't even trigger a DOS most of the time yet we see hundreds of db connections. We are trying this in a test environment, so the increases TPS by 500% and 5 TPS does not trigger the DOS.

 

I can only trigger the DOS by putting the TPS at 1 and tapping F5, which gives me the CAPTCHA page (when set).