A method of providing network security to a client using a DNS, Domain Name System, server arranged for translating domain names to IP, Internet Protocol, addresses, a network security system having assigned a range of IP addresses through which the network security system is accessible, and a database storing a plurality of records each including a domain name and an IP address, the method comprising: receiving (210, 400), at the DNS server, a query from the client to resolve a domain name; selecting by the DNS server an IP address from the range of IP addresses assigned to the network security system; and sending (240, 430) the selected IP address from the DNS server to the client and writing (220, 420, 500-510) mapping data to the database, the mapping data associating the domain name with the selected IP address; receiving (250, 600), at the network security system, a request from the client to access a resource at the selected IP address; sending (260, 520, 610) a query from the network security system to the database, the query identifying the selected IP address; receiving (270, 550, 620), at the network security system, from the database the domain name stored in the mapping data as being associated to the selected IP address; and reissuing (280, 640), by the network security system, the request to a server representing the received domain name, and if there is any response data generated by the server, sending (290, 660) the response data to the client, wherein the method further comprises: applying (630, 650), by the network security system, at least one security and/or filter mechanism to one or more of the domain name, the server's IP address, and/or the response data; and refraining from performing one or both of the steps of reissuing the request to the server and sending the response data to the client, if the at least one security and/or filter mechanism indicates that at least one predefined security and/or filter condition is met. receiving (210, 400), at the DNS server, a query from the client to resolve a domain name; selecting by the DNS server an IP address from the range of IP addresses assigned to the network security system; and sending (240, 430) the selected IP address from the DNS server to the client and writing (220, 420, 500-510) mapping data to the database, the mapping data associating the domain name with the selected IP address; receiving (250, 600), at the network security system, a request from the client to access a resource at the selected IP address; sending (260, 520, 610) a query from the network security system to the database, the query identifying the selected IP address; receiving (270, 550, 620), at the network security system, from the database the domain name stored in the mapping data as being associated to the selected IP address; and reissuing (280, 640), by the network security system, the request to a server representing the received domain name, and if there is any response data generated by the server, sending (290, 660) the response data to the client, wherein the method further comprises: applying (630, 650), by the network security system, at least one security and/or filter mechanism to one or more of the domain name, the server's IP address, and/or the response data; and refraining from performing one or both of the steps of reissuing the request to the server and sending the response data to the client, if the at least one security and/or filter mechanism indicates that at least one predefined security and/or filter condition is met. applying (630, 650), by the network security system, at least one security and/or filter mechanism to one or more of the domain name, the server's IP address, and/or the response data; and refraining from performing one or both of the steps of reissuing the request to the server and sending the response data to the client, if the at least one security and/or filter mechanism indicates that at least one predefined security and/or filter condition is met.