Cyber attackers are very skilled at infiltration. They’d find ways into a house through cracks and holes that the homeowner doesn’t know about. Analogically speaking, that’s what the new cyber attack group dubbed “Hafnium” did when they identified several zero-day Microsoft Exchange vulnerabilities to get into target networks.

With thousands of users for every Microsoft Exchange server, the attack has far-reaching implications. First, it establishes the presence of a new threat actor group in town. What else could they be up to?

Second, the zero-day attack calls for immediate patches for affected organizations. Finally, it brought to light another essential question: What other zero-day vulnerabilities are there?

A Deep Look into the Hafnium IP Addresses

Several cybersecurity experts and organizations, including Malwarebytes and Info Tech, released the attack’s technical details. VirusTotal also mapped out several nodes related to the Hafnium threat actor group.

From all these sources, we extracted 92 malicious IP addresses, then used domain and IP intelligence sources to glean insights into the following:

• IP netblock ownership
• IP geolocation
• Domain associations

IP Netblock Ownership

Tracing which IP netblock a malicious IP address belongs to can help identify the entities administering it. Such knowledge could make the takedown process easier.

The Autonomous System (AS) names and NETNAMEs of the Hafnium IP addresses indicate most of them are owned by cloud service providers and telecommunications companies.

In fact, eight of the top 10 entities associated with the 92 IP addresses are part of the telecommunications industry. One is a cloud computing company, Digital Ocean, which also manages 26% of the blacklisted IP addresses in this study. Another owner is a tech solutions company.

IP Geolocation

The Hafnium group is believed to be from China, although they lease servers in the U.S. as well. IP geolocation details support this, as 21 of the IP addresses are geolocated in China, and several of the top 10 geolocations are neighboring countries. Still, attributing the attack to threat actors from a particular country is not straightforward.

Domain Associations

Passive Domain Name System (DNS) data suggests that at least 25% of the IP addresses are dedicated, having only 1-11 associated domains each.

One noteworthy IP address is 211[.]56[.]98[.]146, which has been identified as an indicator of compromise (IoC) related to the Microsoft Exchange Server zero-day attack. Only one subdomain resolves to the IP address—c3kr[.]simonxu[.]cc.

While this subdomain and its root domain have been tagged “malicious” on VirusTotal, some simonxu[.]cc subdomains are still deemed clean. The following are a few of the subdomains, along with the IP addresses returned by DNS lookups:

These IP addresses and their netblocks are not among the initial Hafnium-related addresses under study, but they seem to share similar characteristics, such as being dedicated and assigned to telecommunications companies.

Aside from applying vulnerability patches as they are made available, security teams could, if applicable, limit or altogether prevent network communications with unknown and suspicious IP addresses. Such an action may be prudent, especially since the Hafnium cyber attack group could have more IP addresses and domains in their arsenal, besides those already published.