Software vendor Citrix is asking all customers to reset their passwords for the GoToMyPC remote access service after it suffered what appears to be a full credentials compromise.
In its advisory, Citrix said the GoToMyPC service had "unfortunately" been targeted by "a very sophisticated password attack".
Citrix provided no further details of the hack, but apologised "for the frustration this is causing".
Apart from requiring GoToMyPC customers to reset their passwords, Citrix also encouraged its users to enable two-step challenge and response verification for their accounts.
Citrix is yet to detail how many users are affected by the breach.
GoToMyPC is one of the oldest remote access solutions. Originally built for Windows, it was first launched in 1998 and is marketed to individual users, IT professionals and corporates, and other large organisations.
The company was acquired by Citrix in December 2003. Over the years, Citrix has expanded the GoTo family of products to include services such as GoToWebinar and GoToMeeting.
Last year, Citrix announced it would spin off the entire GoTo range of products in a reorganisation to be completed by the middle of 2016.