GhostDNSbusters (Part 2)
Illuminating GhostDNS Infrastructure
This research was undertaken in collaboration with Manabu Niseki (@ninoseki on Twitter) and CERT.br (https://cert.br).
Manabu is a Tokyo-based researcher who has been tracking GhostDNS for a number of years. His leads and insight into GhostDNS assisted in confirming the findings documented in this blog post.
We will continue to collaborate with CERT.br on a shared goal of identifying the threat actors operating the infrastructure detailed in this blog.
This post picks up where we left off in our September 8, 2020 blog post titled “GhostDNSbusters”. In that post, we identified:
IP addresses being used by miscreants to compromise home routers
IP addresses of rogue DNS servers
Domain names affected by those DNS servers, directing users to phishing pages
This post will provide details on newly identified GhostDNS infrastructure, provide information about the phishing servers in use, and enumerate additional domain names targeted by miscreants.
During the process of identifying active GhostDNS-related infrastructure, we observed several distinct “groups” of servers. Most involve a single DNS resolver and a single HTTP server used to host the phishing pages. However, one group uses six different DNS resolvers and two HTTP servers, and changes the HTTP servers on a weekly basis.
14-MAY – current
Two, which rotate each Monday.
For the week of Oct 5:
18-AUG – current
12-SEP – current
10-SEP – 23-SEP
08-AUG – current
Table 1: List of recently active GhostDNS infrastructure
The bottom four groups shown in Table 1 are configured in a similar way. Each has a single DNS server, which acts as authoritative for a distinct list of targeted domain names. When the domain name, or select hostnames within them are queried, the servers respond with the IP address of their associated phishing HTTP server. That response has a “time-to-live” of 10800 (measured in seconds, which is three hours).
For example, here are some example queries and results from the “EDA” group, starting with one of the targeted domain names:
Figure 1: Example query for a domain poisoned by the “EDA” DNS server
A query for the “www” hostname within that domain will also point to the phishing IP address:
Figure 2: Example hostname query for a domain poisoned by the “EDA” DNS server
However, DNS wildcards are not used by this group, as seen here:
Figure 3: Example NXDOMAIN query for a domain poisoned by the “EDA” DNS server
In the figure above (Figure 3), we see that the “img.americanas.com.br” query isn’t directed to the phishing server. Instead, a NXDOMAIN response is returned, which indicates that the hostname does not exist. (In reality, that hostname does exist, but since this DNS server is (maliciously) configured to be authoritative for the americanas.com.br. zone (domain), but doesn’t contain a record for the “img” hostname, and isn’t configured to perform DNS wildcarding, it returns an NXDOMAIN response.)
In contrast to the behavior observed by the other infrastructure groups, the CDD group takes a different approach. For all DNS zones that the DNS server is configured to answer authoritatively for, any hostname query will return a response with the IP address of a phishing HTTP server. Here’s an example:
Figure 4: Example wildcard response for a domain poisoned by a “CDD” DNS server
Also unique to the CDD group (compared to the four others mentioned in this blog post) are the weekly rotation of phishing servers, and the availability of SSL/TLS on them. CDD’s phishing servers have a self-signed x.509 certificate that is reused when they rotate in new phishing servers. The x.509 certificate in use recently changed, presumably because it was due to expire soon.
Certificate observed prior to 2020-09-24:
subject= /C=BR/ST=SAO PAULO/L=OSASCO/O=Google. Inc./OU=Principal/CN=SAY MY NAME/emailAddressfirstname.lastname@example.org issuer= /C=BR/ST=SAO PAULO/L=OSASCO/O=Google. Inc./OU=Principal/CN=SAY MY NAME/emailAddressemail@example.com serial=D7AF0B2CBAD8370B firstname.lastname@example.org notBefore=Oct 8 23:28:42 2019 GMT notAfter=Oct 7 23:28:42 2020 GMT MD5: FCB3ECAA96C6A9026CD933281A30551F SHA1: 4E04C2D45F37D7D4E757C27A0A0735B503F319E4 Certificate observed after 2020-09-24:
subject= /C=BR/ST=CATARINA/L=SUL/O=SULAMERICA/OU=SULAMERICA APPS/CN=MANITO MIGUELITO/emailAddressemail@example.com issuer= /C=BR/ST=CATARINA/L=SUL/O=SULAMERICA/OU=SULAMERICA APPS/CN=MANITO MIGUELITO/emailAddressfirstname.lastname@example.org serial=B7BDA9E48E5D2B43 email@example.com notBefore=Sep 24 19:44:55 2020 GMT notAfter=Sep 24 19:44:55 2021 GMT MD5: EE8CF31BE39C5BC046BF5EB25FDACC80 SHA1: 8D9B394BA67D1913566115094C1AD0257FEFF26E This reuse of x.509 certificates allows us to identify new and historical phishing servers used by this group, as we can use Augury to show us where/when this x.509 certificate has been observed.
Similar to the earlier blog post in this series, Passive DNS (PDNS) and DNS Query datasets from Augury were utilized in order to provide further context around the nature of the requests being targeted by the attackers – for which their rogue DNS servers provide redirects to phishing pages. Each group has a unique list of domains that are hijacked. The following is a list of targeted domain names in use by recently-active GhostDNS servers, broken down by the “Internal Name” indicated earlier in this article:
Table 2: List of domains targeted by each active GhostDNS infrastructure
EXAMPLES OF REAL SITE VS. PHISHING SITES
Here, we show a snapshot of the real Web site for banco.bradesco, as it appears in Internet Explorer 11:
Figure 5: Snapshot of the resulting page when typing “banco.bradesco” into IE11 and pressing Enter
We did not specify HTTPS when accessing the page – we simply typed banco.bradesco into the address bar and pressed Enter. As seen in the above screenshot (Figure 7), the address bar shows that we were taken to an SSL-encrypted URL. Also, because the address bar is highlighted in green, we know that the SSL (x.509) certificate presented for this session is a valid, EV certificate, issued by a trusted certificate authority.
When the same action (typing banco.bradesco into the address bar and pressing Enter) is taken, but using the phishing server in use by the “EDA” group, the result is a non-encrypted page, using an outdated background, copied from the banco.bradesco site:
Figure 6: Snapshot of the banco.bradesco page, as served by the “EDA” group phishing server
As seen in Figure 8, the page served by the “EDA” phishing server does not show an SSL-enabled connection in the address bar. A similar experience is observed when performing the same action, but using the “CDD” group phishing server:
Figure 7: Snapshot of the “banco.bradesco” page, as served by the “CDD” group phishing server
When using a URL that specifies SSL (HTTPS), the “EDA” phishing server doesn’t respond, as the server is not listening on the port used by HTTPS (443/tcp).
Figure 8: Snapshot of attempting to access https://banco.bradesco/, via the “EDA” group phishing server
Attempting to access the same (HTTPS) URL when using the “CDD” phishing server will cause an SSL certificate mismatch error to be displayed in the browser, as seen here:
Figure 9: Snapshot of attempting to access https://banco.bradesco/, via the “CDD” group phishing server
INDICATORS OF COMPROMISE
NOTE: This list contains GhostDNS-related DNS server and HTTP server IP addresses, as identified as active at some point between our previous GhostDNS blog post (September 8, 2020) and this one. Earlier indicators of compromise are available at the end of that blog post.
Rogue DNS servers 
HTTP Phishing servers