tailieunhanh - Internet Security Cryptographic Principles, Algorithms and Protocols - Chapter 10

Internet Firewalls for Trusted Systems Tường lửa là một thiết bị hoặc nhóm thiết bị điều khiển truy cập giữa các mạng. Một bức tường lửa thông thường bao gồm các bộ lọc và gateway (s), từ tường lửa khác nhau với tường lửa. Đó là một cổng bảo mật điều khiển truy cập giữa các mạng Internet công cộng và một mạng nội bộ (mạng nội bộ tư nhân) và là một hệ thống máy tính an toàn được đặt giữa một mạng lưới đáng tin cậy và internet không tin cậy. Tường lửa là một đại lý màn. | 10 Internet Firewalls for Trusted Systems A firewall is a device or group of devices that controls access between networks. A firewall generally consists of filters and gateway s varying from firewall to firewall. It is a security gateway that controls access between the public Internet and an intranet a private internal network and is a secure computer system placed between a trusted network and an untrusted internet. A firewall is an agent which screens network traffic in some way blocking traffic it believes to be inappropriate dangerous or both. The security concerns that inevitably arise between the sometimes hostile Internet and secure intranets are often dealt with by inserting one or more firewalls in the path connecting the Internet and the internal network. In reality Internet access provides benefits to individual users government agencies and most organisations. But this access often creates a threat as a security flaw. The protective device that has been widely accepted is the firewall. When inserted between the private intranet and the public Internet it establishes a controlled link and erects an outer security wall or perimeter. The aim of this wall is to protect the intranet from Internet-based attacks and to provide a choke point where security can be imposed. Firewalls act as an intermediate server in handling SMTP and HTTP connections in either direction. Firewalls also require the use of an access negotiation and encapsulation protocol such as SOCKS to gain access to the Internet the intranet or both. Many firewalls support tri-homing allowing use of a DMZ network. It is possible for a firewall to accommodate more than three interfaces each attached to a different network segment. Firewalls can be classified into three main categories packet filters circuit-level gateways and application-level gateways. Role of Firewalls The firewall imposes restrictions on packets entering or leaving the private network. All traffic from inside to outside