What was originally designed to be a banking Trojan has now become a versatile malicious code used to deploy a massive botnet, and is considered one of the most dangerous active malware families today.

In an alert published by the U.S. Department of Homeland Security last year, Emotet was described as “among the most costly and destructive malware affecting state, local, tribal, and territorial (SLTT)." Emotet was extremely active in the first half of 2019, until a recent two-month period when the malware family went under the radar (rumor has it that the sudden disappearance was to allow for maintenance and upgrades). Last week, the malware re-emerged with renewed activity spotted by Cofense researchers.

Making connections and finding new indicators is an important part of IOC analysis, and is probably the most enjoyable part as well. Blog posts and reports on new threats will usually mention the indicators seen to be used by the specific malware sample or attack vector analyzed, yet in many cases there is a larger malicious infrastructure behind them just waiting to be uncovered (and blocked!). Sometimes, a whole other malicious infrastructure can be revealed by examining IOCs related to malicious IPs and domains. There are a variety of tools out there that can help analysts investigate indicators of compromise and their infrastructure, and perform enrichment to shed light on related, malicious IOCs.

In this post, we will review some of our Security Research Team’s favorite connection and enrichment platforms.

As mentioned in our previous post on IOC Collection and Sharing, analyzable indicators can be found on a variety of platforms and channels, each with its own level of reliability and information detail. Once an analyst has deemed the collected IOCs suspicious, they can review its background and infrastructure information, such as ASN and passive DNS for IPs, and Whois, resolving IPs, and popularity score for domains. In addition, the analyst can also check if leading security vendors have already deemed the IOC malicious by choosing from a wide array of open-source blacklists. At the end of this process, the analyst will have the information and knowledge required to decide if the inbound and/or outbound traffic to the indicator should be blocked.

In this post we will review free, open-source tools that analysts can use to collect technical and reputation information on IOCs, with a focus on IPs and domains.

The first step in IOC analysis is obtaining the indicators to analyze. Some analysts will opt to stick with one source, and analyze whichever IOCs come their way, while others may search various sources for a specific threat type such as Ransomware, or threat such as Lokibot. Threat exchanges are open and free community platforms for information sharing and collaboration, and are an excellent source for IOCs. Another source for IOC collection which may come off as less intuitive is social media, with Twitter being the best SM platform to find new, relevant IOCs.

In this post, we will describe our Top 5 Free IOC Sources for Analysis.