When an organization as established and trusted as Yahoo gets breached, it seems like there's no hope for the rest of us. And in many ways, there isn't.
Despite Yahoo's perimeter defenses, the company's network was still breached. Not once, but at least twice. This indicates that these attacks were very sophisticated and carried out by highly motivated and well-funded attackers. Although Yahoo's breaches demonstrate that it's virtually impossible to prevent every motivated attacker from getting past perimeter defenses and gaining access to a secure network, there are ways to detect breaches before massive exfiltration can occur.
When it comes to breach detection and response, most enterprises today still rely on sifting through logs from network appliances such as firewalls and web gateways. This includes performing correlation using security information and event management systems to figure out how the breaches occurred.
The Yahoo breach exposed three key blind spots that need to be addressed to detect sophisticated attacks. (Editors' Note: In the spirit of transparency, SS8, the author's company, helps organizations detect and protect against network breaches using some of the concepts described in this article.)
1. Lack of application, identity, device, and geolocation information. Tools like NetFlow can't distinguish between multiple exchanges of information in a traffic flow (for example, an email session), and at best can only provide a summary of the entire flow. They leave out valuable application-specific information such as To, CC, From, and Subject fields in an email, as well as the presence of any potential malicious attachments. In addition, certain obfuscated protocols such as Tor can be difficult to detect on a network, but the ability to identify their presence and investigate these connections is critical to network security.
2. Challenges tied to archiving and network history lookup. Although some tools can store network log data for long periods of time, it remains difficult to access that information quickly for the purpose of cyber investigations such as correlating potentially malicious network activity to an individual device or user. Meanwhile, packet recording tools can provide more granular detail into network data, but the economics of storing full packets over an extended period of time is often cost-prohibitive.
3. Lack of automated workflows for threat detection. The volume of new, constantly-generated threat information, combined with a shortage of skilled cybersecurity personnel, often leads to "log and alert fatigue." This is generally due to a lack of automation for correlating the latest threat intelligence, and tying it to actual events happening on the network. Currently, most cyber investigators still have to manually perform a series of complicated steps to generate useful forensic information from log reports and the limited history of full packet capture tools.
The Yahoo breach, like most advanced cyberattacks, was carried out over a long period of time, with attackers hiding their communications in the normal flow of network traffic. According to the latest Verizon Data Breach Investigations report, dwell time — that is, the length of time an attacker is in a system before being detected — is averaging more than 200 days.
Perimeter defenses have to make point-in-time decisions to allow or block a specific communication. Therefore, it isn't possible for them to detect advanced and persistent cyberattacks carried out over long periods of time. Even though threats can breach the perimeter through a variety of attack vectors, most malicious activity can be still be detected in the network before data exfiltration — the ultimate goal of the attack — takes place.
If we want to prevent protracted infiltrations and exfiltrations, like the one experienced by Yahoo, we need to combine deeper network visibility, including the ability to rewind past activity with constantly updated threat intelligence, and automated workflows. This will allow us to discover indicators of compromise and devices of interest early in the breach cycle, which can be investigated using actual network history to pinpoint a compromise before massive data exfiltration takes place.
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