SSL Decryption Series: Where Should You Decrypt?

 Encrypted internet traffic is on an explosive upturn. According to the Google® Transparency Report: “Users load more than half of the pages they view over HTTPS and spend two-thirds of their time on HTTPS pages.”[1] At the same time, encrypted traffic carried nearly 3.5 million unique malware samples in 2017. In this series, we’ll dive into the case for decryption, including where and how you should enable it to meet your company’s needs.

In my first post of this series, I wrote about the case for decryption and its benefits. Many technical options are available to decrypt traffic on your network, including web proxies, application delivery controllers, SSL visibility appliances and next-generation firewalls. Where it’s best to decrypt SSL traffic depends on which option provides the greatest protection with the least management overhead – in other words, maximum security return on investment.

The Options

Web Proxies

Web proxies are limited to inspecting and securing web traffic, which includes HTTP and HTTPS. They are typically deployed on well-known web ports, such as 80 and 443. If an application uses non-web ports or protocols, web proxies can’t see the traffic, defeating the purpose of gaining complete visibility and control over encrypted traffic on your network. It’s like deploying airport security in only one major airport and leaving the rest exposed.

Application Delivery Controllers

SSL offload is one of the functions performed by Application Delivery Controllers. An ADC deployment requires two separate boxes – one to decrypt traffic and one to re-encrypt. The problem with ADC deployments is that traffic travels unencrypted between the ADC devices, meaning rogue IT personnel or anyone with access to the physical network connecting the devices has easy access to the data. An adversary can simply port mirror and run a packet capture to retrieve sensitive data in clear text. This undermines the promise of complete confidentiality that is one of the fundamental purposes of encryption and may also violate compliance laws in some industries and geographies.

SSL Visibility Appliances

SSL visibility appliances decrypt traffic and make it available to all other network security functions that need to inspect it, such as web proxies, data loss prevention systems and antivirus. The problem is that these devices increase capex and opex. In addition to the one-time cost, an SSL visibility appliance becomes yet another device in the network that needs to be managed, maintained and updated, with a configuration and rule base entirely different from other security devices. Instead, if one security device is used to decrypt traffic and broker it to all other complementary devices, there is no need to add SSL visibility appliances.

Next-Generation Firewalls

NGFWs include security functions such as application and user control, intrusion prevention systems, URL filtering, network antivirus, and advanced malware analysis. Customers are using firewall refresh opportunities to consolidate multiple security devices into an NGFW to take advantage of the cost savings, enhanced security and ease of managing a single device. In addition, reducing devices and consolidating security functions reduces the complexity and time consumption of troubleshooting since the network topology is far simpler.

NGFWs are the most suitable devices to decrypt traffic, providing several advantages:

1. Decrypted traffic is stored in memory and not sent to other devices. This preserves SSL’s promise of confidentiality and meets compliance regulations.
2. NGFWs can see and decrypt traffic on all ports, providing visibility into all applications, users, content and threats.
3. By consolidating multiple functions into a single device, an NGFW provides enhanced security. For example, it can block known threats using vulnerability protection, antivirus and anti-spyware signatures, and by blocking malicious websites. It can also send new potential threats to the advanced malware analysis environment. If threats are identified, new protections can be delivered and distributed globally within minutes.
4. An NGFW can broker decrypted traffic to other complementary devices as appropriate, such as for long-term retention of logs in forensics appliances.
5. NGFWs provide an easy-to-use management interface that reduces complexity and OpEx. For example, you can combine applications, users, content, URLs, threat prevention and advanced malware analysis into a single rule.

In my next post, I’ll dive into NGFW buying criteria for your decryption needs. In the meantime, please take a look at our recent on-demand webcast and SSL Decryption Whitepaper.

[1] https://transparencyreport.google.com/https/overview?hl=en