The ERIS Ransomware was originally spotted in May 2019 by Michael Gillespie. Over the weekend, exploit kit researcher nao_sec spotted it being distributed through a malvertising campaign using the RIG exploit kit. Using the exploit kit, vulnerable victims will find that the ransomware is installed on their computer without their knowledge simply by visiting a web site. When the ERIS ransomware is downloaded, it will encrypt a victim’s files and append the.ERIS extension as shown below. At this time there is no way to decrypt files encrypted by ERIS for free.
Source: https://www.bleepingcomputer.com/news/security/rig-exploit-kit-pushing-eris-ransomware-in-drive-by-downloads/