Virtual Private Networks (VPN) have become essential for companies that need to cover a wide geographical area without incurring significant set up expenses. A VPN allows remote computers to access the internal corporate network using low cost resources, such as the Internet. The VPN also guarantees the confidentiality of the data send through it by encrypting them at source and decrypting them when they reach the recipient. However, VPN5 cannot guarantee that the information is free from viruses and other threats. This paper describes the characteristics and types of VPN, the main prevention mechanisms and techniques applied by VPNSecure to protect VPNs against malware and hacker attacks.