Hi,
The numbers for this are slowly increasing My iMessage has been hacked
There are 154 replies in that Thread.
In the total number is Apple Devices that use an Apple ID in iMessages out there this is still a small number.
In that thread I have raised the issue with the Hosts.
Change your Apple ID Password for the one used with iMessages (that might also be you ID in other apps and iCloud)
Check the Apple ID site to see if the device is listed (in the other thread this does not seem to happen).
In the other Thread people who have not been doing so have started to use 2 Step verification (needs an Messages app Specific Password).

8:02 pm Saturday; October 15, 2016
iMac 2.5Ghz i5 2011 (Sierra)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
iPhone 6 iOS 10.x and an iPad (2)