Isolated individual computers are relatively secure as long as their physical well-being is ensured and regular backups are carried out to protect the integrity of the data held. However, once computers are connected to a LAN or WAN, they become exposed to threats which may jeopardize their proper operation and the safety and privacy of the data held.

An organisation connecting its computers to a network should therefore take measures to protect its equipment, and users, against attack. The particular measures required will vary according to local conditions and which services the organisation wishes to access and offer across the network. On a LAN such measures represent good practice; when connecting to a WAN such as JANET, they are essential. JANET and the Internet contain a huge and diverse community of users. Both the opportunities and threats presented by this community need to be considered.

Each organisation connecting to JANET should consider how to address issues such as

• developing local security and acceptable use policies
• improving users' awareness of their responsibility and ability to protect themselves and others
• configuring networks and systems to improve security
• use of technical measures such as firewalls, filters and intrusion detection systems
• developing processes, tools and skills to detect, investigate and recover from security incidents.