In our last post we introduced you to APT3 and promised to identify the individuals behind the intrusion. Today we will follow the trail left by APT3’s infrastructure procurers and will identify our first APT3 operator, Mr Wu.

Mr Wu

The trail starts in 2010, when FireEye researchers analysing the Pirpi backdoor used by APT3 identified a sample that communicated with the domain twadcorp[.]com. WHOIS information from late 2009 for this domain gives a registrant name: “Mr Wu”.
Historic WHOIS data showing “Mr Wu” as registrant of twadcorp[.]com
Mr Wu is not a particularly unique name – in fact “Wu” is the 9th most common surname in China. But if we follow the trail ever further back in time we can also identify Mr Wu’s given name.

From APT3 to mxmtmw

To continue the investigation, we need to examine a second Pirpi sample, this time one that communicates with the domain grayflag[.]net. WHOIS information for the domain from 2009 gives the email address mxmtmw[at]
Historic WHOIS showing mxmtmw[at] as a contact for grayflag[.]net
To confirm that we’re still on the trail of a Cyber actor, the e-mail address also appeared in an online advert in Chinese for Trojan development.

Advert in Chinese offering development of customised Trojans

Luckily for us, the string “mxmtmw” is fairly unique online and has also appeared elsewhere, including in a group called Ph4nt0m in 2008, a year before the Mr Wu registration entry for twadcorp[.]com above. In one of those posts the mxmtmw string was used as the username of a poster, part of whose email address is visible in the archives as wuyin…[at]

Google Group entry associating “mxmtmw” with wuyin…[at]
Continuing our journey back in time, a search on the wuyin partial email address reveals other posts related to the same partial address. In one posting from 2007, the poster used a username more helpful to our cause: “wuyingzhuo”. Might this be the same Mr Wu?

Google Group entry showing poster wuyin…[at] using username wuyingzhuo
From mxmtmw to wyz5678

Two further domain name records can be used to confirm Yingzhuo as Mr Wu’s given name.

Returning to the mxmtmw e-mail address, it also briefly appeared in registration data in mid-2011 for the domain grayhat[.]cn. Another e-mail address that was associated with the same domain (it appeared both before and after mxmtmw in the data) is wyz5678[at] “wyz” possibly stands for “wuyingzhuo”, the name we found in Google Groups.
Historic WHOIS showing relationship between mxmtmw and wyz5678

The wyz5678 e-mail address also appears in registration information for another domain-name: ciscocorp[.]com which may lead us to a possible location for APT3.

Infrastructure in Guangdong, China

DNS analysis of the ciscocorp domain shows that ssl3.ciscocorp[.]com previously resolved to IP address 59.42.254[.]195. That IP is owned by “guangdong guangxin tongxin fuwu you”, which translates into English as the “Guangdong Guanxin Communications Services Company”, a wireless telecommunications services company in Guangdong, China. This is possibly an ISP used by APT3 and may give some clue as to the location of the group.
Historic DNS resolutions pointing to 59.42.254[.]195
Wu Yingzhuo

As shown above, similar sub-domains of two other domain names – httb[.]net and caelate[.]com – have also previously resolved to the same IP address. This is significant because the registered name in 2011 for both domains was “yingzhuo wu”.
Historic WHOIS for showing the registrant as yingzhuo wu

In summary, it is possible to follow domain name registration data from APT3 tools and domains to Wu Yingzhuo. Wu Yingzhuo might live or work in Guangdong, China, and has expressed an interest online in Trojan development.

We intend to continue the trail from httb[.]net and to introduce you to a second member of APT3. Read our next post for more truth behind this intrusion.