Three methods to protect DNS servers against malicious attacks

DNS stands for the DomainNameSystem domain name resolution system. In general, DNS is a resolution service that helps users find the corresponding names and IP addresses on the Internet. To make it easier to use network resources, DNS provides a method to associate a computer or service name with an IP address. The name must be easier to understand and remember than a dry IP address. Most users prefer to use an easy-to-remember name such as www.51cto.com) to find the email server or webpage server on the network, rather than the IP address. When a user enters an easy-to-remember DNS name in the application, the DNS Service resolves the name to its value address.
 
DNS resolution is the actual addressing method for most Internet applications. Its appearance perfectly solves the problem of the combination of Enterprise Services and corporate images. The company's DNS name is the identity on the Internet, is a unique identifier resource that cannot be overwritten. The globalization of the Internet makes the DNS name the most important resource to identify an enterprise.
 
However, important resources may be of interest to people. With the occurrence of DNS attacks on the Internet, DNS security issues have become the focus of attention. The common methods are as follows:
 
1. Malicious attacks against DNS systems: dns ddos attacks cause DNS name resolution paralysis.
 
2. DNS name hijacking: Modify registration messages and hijack resolution results.
 
When the DNS server encounters a malicious DNSSpoofing attack, both normal DNS query packets and abnormal packets are routed to the internal DNS server through UDPPort53. in addition to normal packets, when the number of packets per second reaches a certain level, the DNS server cannot handle these junk packets. At this time, normal packet requests cannot receive a normal response, when the IP address of the query website cannot be returned, the user cannot connect to the website and cannot see the webpage. If the query email server is used, the email cannot be sent, important information cannot be smoothly transmitted. Therefore, it is very important to maintain the normal operation of the DNS service.
 
To address the above problems, AX has a solution, that is, the DNS application service firewall. AX has three powerful methods in this issue, which can effectively mitigate the impact of these attacks,
 
1. First, Filter non-DNS protocol packets Malformed Query Filter)
 
2. Then, Cache the information queried through the DNS server)
 
3. If a large number of normal queries are encountered, AX can start the Connection Rate Limit per second)
 
Malformed Query Filter:
 
This abnormal packet is usually used to increase the bandwidth of the external network. Of course, it will also make the DNS server busy, so AX filters such packets on the first line, correct packets are transmitted to the backend servers. Abnormal packets are automatically filtered out to avoid server load.
 
DNS Cache:
 
When the DNS query response returns to AX, AX can pre-set which domains need to be cached and which do not need to be cached. If there is a Cache, when the next same query comes to AX, AX can directly respond from the Cache without having to query on the DNS server. On the one hand, it reduces the burden on the DNS server, and on the other hand, it accelerates the response speed.
 
In addition, when an enterprise chooses this function, it is better to set only the company's Domain as the Cache, and the query that does not close this Domain will not be cached or refuse to respond, this can effectively protect the enterprise's DNS servers.
 
ISP and other services that require a large number of queries are more suitable for using this function, providing better and faster responses to DNS services.
 
Connection RateLimit:
 
When the queried Traffic reaches a certain level, for example, if the same Domain has more than 1000 requests per second, the connection control per second can be enabled on AX, control the number of queries sent to the backend DNS server. If the number of queries exceeds the limit, the server is directly discarded to strictly protect the resources of the DSN server.
 
I believe many people are looking forward to seeing innovative network technologies in the ever-changing Internet and providing better network application services. It is correct to ensure the continuous operation of DNS services and make the information provided by DNS services, which is also the basis of all network application services.
 
This article mentions the DNS Firewall Application Service function. In addition to reminding readers of the importance of the DNS service, we also hope that readers can understand the security of DNS and how to protect DNS servers, it also provides some effective help to prevent malicious attacks.