Resolved: Service Impact Notification for Firewalls Using App Control
Update as of 7/4/19 2:30 pm EST: The signature (SID 6855) has been removed from the Ultrasurf application. If you continue to experience issues with blocked apps/websites please update the App Control database by logging into the firewall and navigating to MANAGE | Rules | App Control and click Update.
Status: Investigating July 4, 2019, 2 a.m. EST
Issue: Skype, MS Teams, Slack and other applications may be blocked by App Control Signature ID 6855 - PROXY-ACCESS Ultrasurf.
Cause: A new signature was released to block Ultrasurf but this is impacting other applications.
Workaround: Please see the following article which provides steps to temporarily disable Signature ID 6855: Skype and MS Teams blocked by Ultrasurf signature