An investigation has been launched at the airport after a memory stick with security details that included the Queen's route to the airport was found by a member of the public.
Details of other confidential security plans were found on an unencrypted memory stick, in Ilbert Street in Queen's Park, west London, according to The Sunday Mirror.
The paper says the USB stick, which had 2.5GB of data, was given to them and contained files revealing information such as security measures used to protect the Queen at the airport, the types of ID needed to access restricted areas and the locations of CCTV cameras and tunnels linked to the Heathrow Express.
Heathrow airport has said it is confident it remains "secure" despite the serious data breach.
A spokeswoman for the airport said security plans had been reviewed in light of the incident.
She said: "Heathrow's top priority is the safety and security of our passengers and colleagues.
"The UK and Heathrow have some of the most robust aviation security measures in the world and we remain vigilant to evolving threats by updating our procedures on a daily basis.
"We have also launched an internal investigation to understand how this happened and are taking steps to prevent a similar occurrence in future."
