Recently some of Dahua DVR’s with old firmware being hacked. They lost the feed of the cameras and instead of a picture, users saw black screen with a “hacked” word at the bottom of it.
Recently all Hikvision and Hikvision OEM brands (Such as LTS and OCULUR) has been affected from the backdoor vulnerability. Hikvision's official notice states the backdoor issue exists in devices with older firmware (firmware released before 2017). The back door is removed in the firmwares released after 2017.