Detica, a security technology firm, has seen its shares rise after receiving an informal bid approach from BAE Systems.
The technology company has been valued at about £450m.
It is understood that Italy's Finmeccanica and US groups Lockheed Martin and Northrop Grumman may also be interested in making a bid. Bidders are also likely to be defence contractors, such as BAE Systems, or IT services companies.
The company generates around two-thirds of its revenues from national security, with the rest coming from telecoms and financial services.
Detica's value to interested parties increased when it became part of the "Trusted Borders" consortium of companies led by Raytheon Systems. The firm recently secured the contract for the next part of the Government's e-borders programme, which will provide security forces with prescreening tools to check people entering Britain.
The additional contract is worth £25 million, most of which will be realised over the next four to five years.
Established in 1971, Detica is based in Guildford with UK offices in London and Cheltenham. Detica has 1,500 employees with staff also in Amsterdam, Geneva and the United States.
