A Russian malware planted from a server in Nigeria was used for a recent cyber attack on Oil India's (OIL) system in Assam's Duliajan, which had brought down the PSU major's network, a top police official said on April 22.

The OIL system is yet to be restored completely even after 10 days of the incident, they added. A top police official, who wished not to be named, told PTI.