According to the Times, the exchange enlisted the services of the British secret services to investigate an attack on its headquarters, which is believed to have taken place at some stage in 2010.
Hackers are thought to be based in Russia and could also have been involved in a cyber attack on exchanges in the US, the newspaper reported.
The reports follow the release of a statement by the LSE earlier in January which claimed that an outage which affected its Turquoise trading platform towards the end of 2010 was due to âhuman errorâ and did not take place under suspicious circumstances as the exchange had originally claimed.
In a statement, the LSE said: âThe exchange can confirm that its internal investigation into last November's trading disruption on Turquoise has now concluded.
"The investigation found the incident was the result of human error and the incident has now been closed.â
The outage has set back the LSEâs adoption of the Millenium ITâs trading platform until later this month.