Companies are being warned of the dangers posed by third-party web transfer services, and the use of instant messaging and social networking sites to send personal information.

This is despite recent high profiles cases which have highlighted the dangers of using postal services to transfer personal data.

Software developer and hosted back-up firm DVS Soft Distribution said that the methods some employees use to transfer large files are putting organisations at serious risk of data leakage and possible malware contamination.

"Restricted by email attachment size and even file formats, ever resourceful employees are finding other ways to transfer large files and most of them are even more insecure than email," said Andy Hansen, sales manager of DVS Soft.

"The average business may not be transferring vast quantities of customer information, but it is still likely that typical files will include sales information, market projections, confidential pitches and competitive analysis.

"This is not the sort of information that most businesses want out in the open."

Hansen believes that the majority of employees use external services in the genuine belief that it is helping them to be more efficient and are not intentionally putting their employer at risk.

But, aside from the increased risk of information theft or a delivery mistake by the postal company, there is also the distinct possibility that the file or the site on which it is hosted may be compromised by malware.

"One of the problems is that businesses have restricted employees' ability to send large files over email without recognising that they still need to be able to get that information to partners and customers," said Hansen.

"Consequently employees just look for the easiest and most familiar method out there which is often social networking sites and web 2.0 tools such as instant messaging.

"Reputation is often underestimated in business until you've lost it, of course.

"Companies need to ask which looks more professional: a dedicated, fully encrypted, password protected file system that can be accessed via the web; or sending your best customer to 'www.acme-toobigtosend.com' to download a file."