Category: Malware

Investigating A Malicious Attachment Without Reversing

Do you need to be a hardcore malware reverser to understand how malware works under the covers? No, not always. Here’s an example of using some free tools and OpenDNS Investigate to expedite the analysis process and rapidly protect your organization.

Subject: Urgent Notification N443111645
Thank you for placing order with our company now! Your purchase is processing right now.
Outright Purchase: 4200 AUD
Please check the statement given with this email to see more details about your order.

Purchase Number: AGS873904473
Order Date: 12:45 Monday, Mar 2 2015
Customer Email: <victim email address>

Attached to the email is a Microsoft Compiled HTML Help file (.chm) that, according to VirusTotal at the time of this writing, has been uploaded 28 times since 2015-03-02 23:11:38.

Screenshot 2015-03-02 21.52.22

The file most commonly utilizes the pattern payment_ddddd.chm, where ‘ddddd‘ is a seemingly random generated integer five digits in length.

Screenshot 2015-03-02 21.50.01

Full dynamic analysis of this file can be viewed here:

When executed, the .chm file downloads an executable named tv.exe from www[.]igloofire[.]com. The tv.exe file generates domain names using a DGA, tries to resolve the domain names, and finally contacts those domains with a single HTTP GET request and 20 HTTP POST attempts. The VirusTotal dynamic analysis for the tv.exe file can be viewed here:

“But Andrew,” you ask, “how do you know that? We don’t see anything in the VirusTotal analysis to substantiate that.”

Screenshot 2015-03-03 08.03.47

That’s absolutely correct. In fact, the dynamic analysis from VirusTotal only shows communication to on UDP port 123 – which is a Microsoft NTP server that the Windows virtual machine likely called out to in order to sync its time.

This exact situation illustrates some of the issues with relying entirely on dynamic analysis engines. That being said, we strongly suggest that you try multiple engines/platforms when performing dynamic analysis to see what shakes out. One alternative is The Shadowserver Foundation’s platform. Analyzing the downloaded tv.exe file on ( shows us that several signatures have been trigged.

Screenshot 2015-03-03 08.55.19

As well as interaction with the DGA in question – perviylich[.]ru

Screenshot 2015-03-03 08.55.09

Additionally, we can observe the system level communication flow and the Windows hooks involved in said communication.

Screenshot 2015-03-03 08.12.14

Now reversing the malware would have eventually given us this domain but we’re in triage mode right now. We can always reverse the malware later to confirm and/or expand our findings.

Looking up the perviylich[.]ru domain in OpenDNS Investigate, we can tell several things:

1) The domain is blocked by OpenDNS

2) The domain only recently became active

Screenshot 2015-03-03 08.18.52

3) The majority of clients requesting the domain are from Australia (80%) – perhaps a targeted attack on a particular region?

Screenshot 2015-03-03 08.21.15

4) The threat model identifies this domain as having a high likelihood of being a DGA

Screenshot 2015-03-03 08.22.50

5) The domain utilizes the following IP addresses: (also the name server) and

Screenshot 2015-03-03 08.24.12

6) The IPs are allocated to AS’ in Ukraine and Russia, respectively

Screenshot 2015-03-03 08.26.00

Screenshot 2015-03-03 08.26.47

7) The IP addresses also host a number of other DGA-looking domains

Screenshot 2015-03-03 08.28.56

Screenshot 2015-03-03 08.27.51

8) In looking at some of the other domains on that infrastructure, we can see a similar pattern across the entire hosting IP addresses

9) We can also see a pattern emerge that shows pairings of DGA registrations utilizing the same domain name combined with both a .ru (Russia) TLD and a .su(Soviet Union) TLD.

Screenshot 2015-03-03 08.32.33
Screenshot 2015-03-03 08.32.25
Screenshot 2015-03-03 08.32.18
Screenshot 2015-03-03 08.32.10

10) Using this information, we can create a master list of domains involved in this particular malware infrastructure run:


If you’re a visual person, you can also graph the domains, using the OpenDNS Investigate API and the open source OpenGraphiti tool, to show the linkages. The image below shows the domains (outside edge of circle) and how they’re associated with the two IP addresses found earlier in this post.

Screenshot 2015-03-03 08.44.35

To confirm findings, however, you can (and probably should) analyze the memory of the running binary to ensure that there are no subsequent IP addresses or domains called out to that may have been missed by your dynamic analysis engines. In this particular case, there were no additional domains or IP addresses.

11) Digging even further into the domain list, we can query Investigate for any IP addresses these domains resolved to in the past

Placing the domains into Maltego and using OpenDNS’s Investigate transform, we found two IP addresses these domains resolved to. Both

Both of these IP addresses were also the IP addresses of the domains’ name servers. This add to the suspiciousness of the domain names.

12) Identifying the name server domains, we queried Whois to find more information about the registrant of the name server domains. 

It turns out the email account,, used to register the name server domains also registered a handful of other domain names.

Domain NameCreation Date
dnskkop12.com15-feb-2015 16-feb-2015 03-mar-2015

All of which had similar subdomains of ns1, ns2, ns3, and ns4 and all of which were registered through the notoriously abused registrar and were acting as name servers for fastflux as well as command and control domains.

We dumped all these domains, their subdomain, and their IP addresses into our Maltego graph and found some interesting connections.


13) Noting that YopMail is a free temporary email service, we visited the site and checked the web-based inbox of (the registrant of all these name servers associated with malicious domains)

It turns out the registrar confirmation emails were still there, dating March 1 through March 3. This confirms the whois records.

Screen Shot 2015-03-03 at 14.15.14
Screen Shot 2015-03-03 at 14.14.43
Screen Shot 2015-03-03 at 14.12.41
Screen Shot 2015-03-03 at 14.15.00

14) It should be noted that AS48031 is a rogue AS that has been serving malicious sites for a while in addition to performing various evasive actions.

We’ve been monitoring it for a while and discussed it in March 2014 in this webcast (minute 19:25 in “Rogue and Stealth ASNs”) and at Virus Bulletin here.

AS48031, XSERVER-IP-NETWORK-AS PE Ivanov Vitaliy Sergeevich,UA, that a lot of security folks will recognize has been hosting all kinds of malicious and shady content (malware, browser-based ransomware, porn sites, spam, radical forums) and it’s been “fluxing” on and off the routable IP space. For example, in earlier 2014, it disappeared off the global routing table but as of early March 2015, AS48031 is online and advertising its prefixes by verifying our BGP routing tables and as shown below.


At the time of this writing, there are 1900+ live IPs on AS48031 IP space, and further checking them reveals finer granularity of allocation. A few suspicious small hosters are selling this sub-allocated IP space for customers via VPS, VDS, and dedicated servers. is one of these hosters that warrants further scrutiny. We discussed similar rogue or abused small hosting providers in our recent talks at BlackHat, DefCon and Virus Bulletin.



We wouldn’t be surprised to see a few domains start using as an authoritative zone very soon and can with confidence, say they are domains you don’t want your devices connecting to.

At this point you should have a good idea of how to leverage OpenDNS Investigate to perform detailed malware triage and infrastructure investigations to protect your organization and its users – all without having to open a hex editor or manual debugger.

Until next time!

The post Investigating A Malicious Attachment Without Reversing appeared first on OpenDNS Security Labs.

Great analysis on Clapzok multi-OS malware

The ThingI can’t recall who tweeted it, but an excellent article was published on the analysis of what {W32/Linux/OSX}/Clapzok does. The full article can be downloaded here [Google Drive rendered PDF] and below is the brief intro:

A cross-infector of entirely unrelated platforms is typically implemented as two viruses stuck together, simply because it’s the easiest way to do it. However, if the general mechanics of fi le enumeration and infection are the same across the affected platforms, then a virus can implement an abstraction layer and expose APIs that each of the routines can call to perform the essential functions of find/open/map/unmap/close. This is exactly what {W32/Linux/OSX}/Clapzok does.

The virus begins by calculating the CRC32 of itself. It uses a reverse polynomial (the usual ‘0xEDB88320’) to calculate the hash value. The resulting value is used as the seed for the random number generator in the virus. The virus also relocates the pointers to the abstraction routines, according to the load address of the virus code.

More details can be found here:

The “Less Than Zero Threat”

Interesting article (part 1 / part 2) by Alan Shimel on the concept of the “Less Than Zero Day Exploit”.


From the article:

Once a vulnerability is publicly announced, the zero-day clock starts ticking. The announcement is typically followed by some period of time before a patch is made available. This is the Zero-Day period. According to accepted wisdom, organizations face the greatest danger when an attack or exploit targeting the vulnerability is verified in the “wild.”

Some believe this is a flawed argument. As evidence, they point to “underground” vulnerabilities and exploits that are equally as dangerous and much more difficult to detect and protect against because they are “unknown.” At StillSecure we call this class Less-Than-Zero Threat. The chart below shows the relationship between the Less-Than-Zero threat and the Zero-Day threat and the level of risk they pose to the organization. It also takes into account such factors as responsible disclosure, patch deployment, etc.

The conclusion:

Zero-Day, Less-Than-Zero, patching, exploits…the world is a dangerous place. While our attention has been focused by some security vendors and the press on the Zero-Day attack, the Less-Then-Zero threat is also significant enough to warrant your attention and resources. The reason you don’t hear a lot about this type of attack is because the majority of vendors don’t have a silver bullet to sell you for solving the problem. There is still no substitute for good, old-fashioned, best practices in security.

I completely agree with Alan’s final statement. No product is a substitute for security best practices.

Scroll to top