Supply of the Gootloader touchdown pages reveal various completely different search phrases and phrases the menace actors needed search engines like google and yahoo to index. The linked subpages (chosen with inexperienced) don’t really exist. The injected WordPress code defines a couple of hooks, one in every of them is for non-existing pages. This may serve the faux discussion board dialogue, when the sufferer clicks on the search end result
That hidden factor had hyperlinks (chosen with inexperienced) and the matching focused search phrases (chosen with brown):
This hidden factor won’t be seen to human webpage guests. However search engine crawlers see and course of it, which methods the various search engines into treating the web site as if it gives related content material on the poisoned search time period, thus rating the location excessive within the search outcomes.
A screenshot of the supply code from a Gootkit/Goodloader touchdown web page. Picture courtesy of Sucuri Analysis.
The report (and screenshot) revealed three promising strings:
The request: $_GET[”a55d837’
A malicious web domain name: ‘my-game[.]biz’
A SQL question (proven on a unique screenshot in Sucuri’s weblog): ‘SELECT * FROM backupdb_’
Looking out Google for code fragment $_GET[”a55d837’ led us to an online decoder page, where the result (now deleted) of another researcher’s query revealed the encoded version of the PHP code used in the malicious web page:
function qwc1() {
global $wpdb, $table_prefix, $qwc1;
$qwc2 = explode('.', $_SERVER["x52105x4d117x54105x5f101x44104x52"]);
if (sizeof($qwc2) == 4) {
if ($wpdb - > get_var("x53105x4c105x43124x20105x58111x53124x5340x28123x45114x45103x5440x2a40x46122x4f115x20142x61143x6b165x70144x62137".$table_prefix.
"x6c163x74141x7440x57110x45122x4540x77160x2075x2047".$qwc2[0].
'|'.$qwc2[1].
'|'.$qwc2[2].
"x2751x3b") == 1) {
and the decoded model of that very same script:
operate qwc1() {
world $wpdb, $table_prefix, $qwc1;
$qwc2 = explode('.', $_SERVER["REMOTE_ADDR"]);
if (sizeof($qwc2) == 4) {
if ($wpdb - > get_var("SELECT EXISTS (SELECT * FROM backupdb_".$table_prefix.
"lstat WHERE wp = '".$qwc2[0].
'|'.$qwc2[1].
'|'.$qwc2[2].
"');") == 1) {
Whereas it isn’t clear how the code ended up on that web site, the Web by no means forgets: Search engines like google and yahoo discovered and listed this evaluation. This gave us the primary perception at what the injected code of the compromised touchdown pages would appear to be.
(Each the evaluation linked above, and one other web page I subsequently discovered on malwaredecoder.com, have been later eliminated by their respective web site homeowners. Search outcomes that reveal ephemeral evaluation pages like these are solely obtainable for a brief time period. If you happen to plan to quote supply supplies from websites equivalent to these, hold an offline copy of the web page, as a result of they is probably not there if you return.)
At this level we didn’t know precisely how the websites are compromised, however we knew from the report that malicious PHP code is someway inserted into the WordPress set up.
The search on VirusTotal for content material:”SELECT * FROM backupdb_” offers a few information from a compromised server that include an error message:
WordPress database error: [Table 'interfree.backupdb_wp_lstat' doesn't exist] SELECT EXISTS (SELECT * FROM backupdb_wp_lstat WHERE wp = '117|50|2');
The criminals are possible utilizing the database backupdb_wp_lstat, which will need to have been faraway from the server throughout a cleanup. We have been trying to find this content material on VirusTotal (search time period: content material:”backupdb_wp_lstat”), hoping we’d come upon a database dump. It’s at all times a good suggestion to arrange these guidelines and do further retrohunts, which might reveal different beneficial information or information.
We have been fortunate, and located an archive file containing a SQL dump of the WordPress database from a compromised server on a public malware repository.
The WordPress database dump included this desk that comprises a set of the primary three octets of IP addresses, a block checklist of IP ranges that can’t revisit the Gootloader web site on the identical day
The dumped database comprises a desk known as backupdb_wp_lstat. Later evaluation decided that this desk comprises the IP tackle blocklist the malicious web site makes use of to stop repeat visits.
The obfuscated PHP code was additionally viewable within the database dump:
A block of base64-encoded information saved as a variable named $pposte in a WordPress database
…as was the injected search engine optimisation poisoning content material, with the j$okay..j$okay marker:
Malicious search engine optimisation content material phrases embedded in a WordPress database desk, linking the location to an Excel spreadsheet converter search question
Researchers who wish to hunt for this identifiable string within the Descriptions property of the malicious touchdown pages can use the regex /j$okay([0-9]{1,10})j$okay/
The “place marker” string seems within the OpenGraph metadata search engine optimisation headers of a Gootloader-modified internet web page
This marker serves as placeholder for the spot the place Gootloader’s hyperlink to the web page renderer script is inserted. When the Gootloader web page is served up, it excludes the marker from the web page supply.
Nevertheless, the code extracted from the SQL database dump was not precisely the identical as what was proven within the Sucuri weblog. We continued looking for extra examples by pivoting on the C2 server my-game[.]biz, and located a handful of PHP information referring to that server:
Information that include references to the Gootloader “mothership” web site (screenshot courtesy of VirusTotal)
The submission title commented_functions.php regarded promising. Certainly, it turned out to be possible the work of a researcher, analyzing the PHP supply code from the compromised WordPress set up. It was kindly documented intimately, saving us some evaluation time (which additionally helped as a result of we didn’t have all of the elements).
Commented textual content, preceded with double slashes, paperwork the Gootkit traits of modified internet pages
We have been in a position to make use of the base64 string referenced within the “html” remark above to look VirusTotal, which led us to a (comparatively) not too long ago uploaded SQL dump.
a WordPress database dump in VirusTotal
The dump file contained the beforehand referenced base64 blob…
A SQL dump from a compromised WordPress set up comprises base64-encoded components of the Gootkit/Gootloader modifications
…which, when decoded, output the identical code that was initially revealed by Sucuri:
The decoded base64 information from the WordPress database reveals the PHP script that handles decoding the malicious content material for a web site customer
With this in hand, we had better confidence within the provenance of this malicious code. We additionally recognized the desk the place Gootloader shops it in a compromised WordPress database. Having positioned the dump of the WordPress database and the PHP code on the net decoder web site, now we have an entire copy of the malicious content material hosted on the compromised touchdown websites.
What’s within the touchdown web page code?
This code comprises a easy PHP command shell, which the Gootloader attackers can use to take care of entry to compromised pages.
The variable $pposte holds the title of the parameter that will get executed. If the compromised web site receives an HTTPS POST with that string in it, the code on the web page will decode and execute any base64 encoded instructions it receives, turning right into a bare-bones command shell the attackers can use to take care of management over the server:
A easy command shell Gootloader inserts into the PHP operating in a WordPress web site the menace actors have compromised
At different factors contained in the code, the script defines filters for WordPress occasions, which set off the execution of features based mostly on predefined situations.
For instance, the next operate executes as soon as the attackers have arrange the compromised WordPress setting: the invoked code (referenced as “qvc5”) initializes the backupdb_wp_lstat database desk.
add_action("wp", "qvc5");
This snippet from the qvc5() operate initializes the backend databases utilized by Gootloader:
On getting ready the requested internet web page, the malicious occasion handler hooks construct the request to the “mothership” (a reputation I’ve given to the web site the Gootloader operators use to centrally handle their fleet of compromised blogs). The communication sends the mothership the next parameters of the preliminary request, all in base64 encoded type:
Certainly one of Gootloader’s most problematic behaviors is that it solely permits the potential sufferer to go to the location as soon as in a 24-hour interval. It does this by including the originating IP tackle of this communication (the tackle of the sufferer PC, variable ‘b’ above) to a block checklist. The server additionally geofences IP tackle ranges, and solely permits requests to originate from particular nations of curiosity to the Gootloader menace actor. The referrer string (variable ‘d’ above) comprises the unique search phrases.
(On this instance, the “&d=” referrer string is the base64-encoded worth of “google/?q=cisco_wpa_agreement”)
Later, we are going to see that the server’s response would be the faux discussion board web page renderer code.
The mothership sends the faux discussion board web page
The mothership response comprises two components: one comprises the HTML header components, and the opposite comprises the web page physique content material. The 2 are delimited within the code by a tag.
The header half comprises a number of components, separated by pipe (“|”) characters. Utilizing what it will get from the mothership, the touchdown web page code will collect the HTML content material:
The portion of the Gootkit code that collects the HTML content material of the faux web page it can later draw excessive of the compromised web site
The script provides the whole /24 IP tackle vary the place the request originated to a 24-hour block checklist. Neither the originating laptop, nor any others with the identical preliminary three units of numbers in its IP tackle, can get the web page once more for a minimum of a day. (This was already seen within the SQL database dump):
The Gootkit code blocks repeat guests by including not solely the customer’s IP tackle vary to a block checklist, however the whole class C IPv4 tackle vary on both aspect of the customer’s tackle, only for good measure
How Gootloader renders the faux discussion board web page
If the request comes from an IP tackle that isn’t on the block checklist, the malicious code within the compromised WordPress database takes motion and delivers the bogus message board content material (sometimes titled merely “Questions And Solutions”) to the customer’s browser.
The Gootloader faux discussion board web page, that includes a “query” and an “reply” that hyperlinks to the Gootloader JScript first-stage payload
The one seen malicious content material within the supply code of a compromised touchdown web page is a straightforward inserted JavaScript tag. For instance:
Right here, once more, the distinctive key for the contaminated server is used as a parameter assigned to a numeric worth (1174868 within the above instance):
The distinctive secret is linked in a Javascript code snippet embedded within the compromised WordPress server web page.
This
If the HTTPS GET request comprises a question string that features the an infection ID, the handler code sends a request to the mothership and renders the response.
We’re capable of get the code returned by the mothership by grabbing the faux touchdown web page HTML supply, and utilizing an online debugger that information the on-the-fly adjustments.
First it deletes the unique content material of the HMTL web page:
A set of instructions that deletes from view the unique web page content material on the compromised WordPress server web page the customer lands on
…and replaces it with the faux discussion board textual content…
The alternative content material consists of the textual content of the “Questions And Solutions” faux discussion board web page
…which additionally comprises the obtain hyperlink for the primary stage JScript payload:
The obtain hyperlink factors to a php script hosted on a unique server. This hyperlink delivers the .js file packed right into a Zip archive which includes the primary stage Gootloader payload
The end result will appear to be a dialog within the weblog feedback through which somebody “asks” a query equivalent to the search question handed from the Google referrer textual content, a “response” seems from a person account named Admin with the search time period hotlinked to the primary stage JScript downloader, and a followup “response” from the identical “person” who “requested” the preliminary query, thanking the admin who “answered.”
The complete dialog is a fiction. It follows this sample in each Gootloader incident.
A Gootloader faux discussion board web page in German. The supply code of the web page exhibits the hyperlink factors to a file named down.php hosted on a totally completely different server than the one the place the web page seems. The hyperlink marked in crimson will hook up with the server that’s internet hosting the first-stage obtain JScript.
The primary-stage downloader web site
The faux discussion board web page connects to the primary stage obtain server, the place a PHP script serves the primary stage JScript downloader script.
(We obtained a duplicate of this script from one other researcher within the safety group, who needs to stay nameless, underneath TLP:Pink restrictions. Whereas we couldn’t use the script we obtained on this weblog put up, we might use traits of the script to hunt for comparable samples.)
On the server aspect, this file is embedded as a big Base64-encoded information blob, with textual content that begins:
With this data, we might seek for comparable scripts, utilizing this Yara rule:
rule gootkit_stage1_dl{
strings:
$a = "
This gave us a handful of different variants of the script, with the primary distinction being the obtain URL:
We noticed two mothership addresses, 5.8.18[.]7 and my-game[.]biz within the samples we studied. On the time we initially researched this, the my-game area resolved to that IP tackle (it now resolves elsewhere). Oddly, the compromised touchdown web page code hyperlinks to the area, and the primary stage JScript downloader hyperlinks to the IP tackle.
The primary stage obtain script (down.php or be part of.php or about.php or index.php) merely relays the incoming request to the mothership:
The supply code of the PHP script that delivers the primary stage Gootloader payload
The request despatched to the mothership will return the first-stage downloader JScript packaged in a Zip archive. As a result of it passes the unique referrer string all the best way to the mothership, it can obtain the unique search phrases, and may return a payload with a file title matching these search phrases, which is what we’ve noticed occurs.
How Gootloader compromises WordPress servers
Close to the tip of our preliminary analysis, we discovered an necessary piece of details about the possible supply of the preliminary compromise of the internet hosting WordPress servers. As we collect extra data, it’s price revisiting prior analysis, which can reveal clues that we didn’t know have been associated on the time.
The writeup describes an assault the place attackers positioned a modified copy of the Hey Dolly plugin within the WordPress uploads listing (e.g. wp-content/uploads/), which they then used to provoke the set up of the malicious WordPress content material.
HelloDolly.php has been a inventory plugin, included with the WordPress self-hosted obtain, for a few years. In any case, modifying this code in a comparatively benign plugin, and leaving it in place on the compromised server, permits Gootloader to function in plain sight whereas minimizing the filesystem adjustments that may reveal a compromise to an alert webmaster.
There are a number of methods through which a menace actor would possibly be capable to place a file right into a WordPress web site: The credentials for the online server may need been phished or stolen; a WordPress element could have had a vulnerability that permitted distant customers to carry out SQL injection or command execution exploits on the host server; the executive WordPress password may need been stolen.
On this case, the writeup comprises a screenshot:
Screenshot of the modified HelloDolly.php script (courtesy of the Wealthy Infante weblog)
We searched VirusTotal for extra of those information:
content material:"dolly_css"
Whereas we discovered a number of clear, unique variations of the HelloDolly.php file…
Right here, the malicious HelloDolly PHP script is put in as a WordPress plugin underneath the trail:
wp-contentpluginsHello_DollyHelloDolly.php
One other format of the modified HelloDolly.php script exhibits the distinctive identifier string
The malicious PHP information present the extra code, together with the unique Hey Dolly lyrics. An inserted code will examine the POST request for particular parameters, and if discovered, will execute the submitted set up code.
A variation on the Gootloader-modified HelloDolly.php script
We discovered different variations the place the $dolly variables are renamed $wp
A screenshot that summarizes the modification course of Gootloader makes use of (picture courtesy of the Wealthy Infante weblog)
We discovered these elements within the SQL database dumps, giving us sufficient confidence to determine that this was (a minimum of) a technique the attackers compromised these reputable WordPress websites to show them into distribution servers.
A WordPress database dump comprises the identical components that the Wealthy Infante weblog references
Sadly, as a result of this has all been maintained on a server that’s immediately managed by the menace actors, no matter supply code it might include will not be obtainable to researchers.
Disturbingly, since 2018 when Gootloader first appeared on the scene, it has used the identical area, and for many of that point, the area pointed to a lot of the identical IP addresses.
5.8.18[.]7
The my-game[.]biz area resolved to this IP tackle for a number of years. Most of the malicious scripts level immediately at URLs hosted on this IP tackle to ship elements of the an infection.
Recognized URLs:
http://5.8.18[.]7/filezzz.php
The preliminary elements of the an infection are information generally known as Gootkit. They’re normally simply PHP scripts that include a base64-encoded string and a script to decode the info and output it to a variable, equivalent to this file (variably known as be part of.php or down.php).
The encoded type of a PHP script that delivers the .js payload
We have been additionally capable of establish a number of Gootkit information that confer with, or hyperlink to, this IP tackle, together with this script, and this script. Each of those information include error messages that confer with one thing not with the ability to utterly obtain a element.
A screenshot of a file uploaded to VirusTotal exhibits references to the IP tackle previously used to host the Gootkit/Gootloader “mothership” server
Curiously, the server-side downloader script was named file_tmp_41.php, which is not like the downloader scripts seen usually. Which will point out this script was an artifact of testing.
If we pivot off of this data, and (for instance) search VirusTotal for content material:” . The end result yields furtherinformation, each of which include a URL that we’ve beforehand mentioned:
This was one other tackle that my-game[.]biz has resolved to previously. We have been capable of finding one other first-stage Gootkit element that hyperlinks on to this IP tackle.
91.215.85[.]52
One more IP that has been used to host my-game[.]biz and continues to take action. We discovered nonetheless one other first-stage Gootkit script that hyperlinks to this IP tackle.
my-game[.]biz
The location is clean now, however the Web Archive reveals an attention-grabbing origin story to this area: In 2014, it was used to host a Russian on-line playing web site. Since 2018, the web page has hosted no different content material however has been linked to the Gootkit/Gootloader malware.
The my-game web site because it appeared in 2014, a Russian-language playing web site known as “On line casino Recreation Life”
The one different reference we might discover to the area was a Counter-Strike clan listing courting again greater than 15 years.
The my-game area that continues to host the Gootkit/Gootloader mothership initially belonged to a German group that performed the sport Counter-Strike competitively
The listing lists this web site as the house web page for a bunch of “semi skilled” gamers based mostly in Germany who performed underneath the deal with #mY-GaMe.
Identify: #mY-GaMe
Clan-Tag (Kürzel): #mY-GaMe`
Land (Hauptsitz des Clans): Deutschlandweit
Ort (Hauptsitz des Clans): Deutschlandweit
Chief: pr0nb1tch
ICQ#: 256558686
Homepage: http://www.my-game.biz
Anzahl der Spieler: 10
Artwork der Spielmodi: Leaguez
Clan-Profil: Semi-Profi-Clan
Clan sucht neue Spieler: Ja
Chief: [email protected]
Open-source intelligence reveals quite a bit
With a malware an infection technique seemingly designed to make it as tough as potential for researchers to dig in and study the way it works, Gootloader stays one of the vital pernicious and difficult-to-study threats on the internet.
Nevertheless, regardless of most of its code current and operating inside different individuals’s WordPress servers, the proliferation of on-line evaluation instruments gives a wealthy pool of alternative to learn the way the malware works, and the way its loader delivers payloads. Because of the sources uploaded by quite a lot of completely different analysts and researchers, we’ve been capable of construct a virtually full image of how the malware operates.
The PHP scripts, embedded JavaScript elements, and downloadable JScript payloads of this an infection are actually effectively understood, and but the malware continues to have an effect, greater than six years after it was first found. Thankfully, as a result of comparatively sluggish tempo of the malware’s growth and its comparatively steady internet hosting of the “mothership” server, static and dynamic detections stay efficient.
And a last notice about collaborative analysis initiatives. It pays to develop and keep relationships with the malware evaluation and safety analysis group. For this mission, we obtained assist from a number of researchers, a few of whom didn’t wish to be acknowledged. Our recommendation: If you happen to do this type of work, don’t hesitate to share your findings; you will discover that the trouble you spend money on collaboration with colleagues throughout the business will finally repay if you want data. We’re grateful for the assist and assist we obtained from a number of people.
Acknowledgments
Sophos X-Ops gratefully acknowledges the contribution of Marv Ahlstrom, an search engine optimisation professional who suggested us about numerous features of Gootloader/Gootkit’s malicious search engine optimisation. The writer additionally needs to thank the pseudonymous researchers who use the handles @sS55752750, @SquiblydooBlog, and @GootLoaderSites for his or her help. We additionally acknowledge and are grateful for analysis beforehand revealed by Sucuri and Wealthy Infante. X-Ops researcher Andrew Brandt contributed to this evaluation.