Firewalls and Gateways - I
A firewall is a computer that sits between an institutional network and the potentially dangerous insecure Internet/Outside network.
Firewalls can be taught to filter information by address or by content
- e.g. it could only allow inside-->outside messaging or messages to or from certain sites (this can be fooled by forging network addresses)
- e.g. it can prevent file transfer but accept email
- However email is actually a common file transfer mechanism and postscript (for instance) can easily hide rogue programs
- Often firewalls are highly inconvenient and in mysterious ways handicap legitimate traffic when in fact nobody realizes firewall exists!