index= sourcetype="cisco:asa" (eventtype="cisco_vpn_start" OR eventtype="cisco_vpn_end") src_ip= user=*
| stats earliest_time(user_login) as user_logout_time,latest_time(user_logout) as user_login_time, earliest_time(VPN_login) as VPN_start latest_time(VPN_logout) as VPN_end by user, src_ip
| eval User_On_VPN_minutes = (VPN_end-VPN_start)/60
| eval User_On_Network_minutes = (user_logout_time-user_login_time)/60
| eval perc_On_VPN = (User_On_Network_minutes/User_On_VPN_minutes) * 100."%"
| where perc_On_VPN > 80%
You can replace user_login, user_logout, VPN_login and VPN_logout with your specific events.
Hope this helps, Thanks!
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