Story of a signed, susceptible, ad-injecting driver

Malware analysis entails learning risk actor TTPs, mapping infrastructure, analyzing novel strategies… And whereas most of those investigations construct on current analysis, generally they begin from a hunch, one thing that appears too easy. On the finish of 2023, we stumbled upon an installer named HotPage.exe that deploys a driver able to injecting code into distant processes, and two libraries able to intercepting and tampering with browsers’ community site visitors. The malware can modify or exchange the contents of a requested web page, redirect the consumer to a different web page, or open a brand new web page in a brand new tab based mostly on sure situations.

The installer was detected by most safety merchandise as an adware element however what actually piqued our curiosity was the embedded driver signed by Microsoft. In line with its signature, it was developed by a Chinese language firm named 湖北盾网网络科技有限公司 (machine translation: Hubei Dunwang Community Know-how Co., Ltd), the lack of knowledge about which was intriguing. The distribution technique remains to be unclear however in response to our analysis, this software program was marketed as an “Web café safety answer” geared toward Chinese language-speaking people. It purports to enhance the net shopping expertise by blocking advertisements and malicious web sites, however the actuality is kind of totally different – it leverages its browser site visitors interception and filtering capabilities to show game-related advertisements. It additionally sends some details about the pc to the corporate’s server, most certainly to collect set up statistics.

On high of its apparent mischievous habits, this kernel element unintentionally leaves the door open for different threats to run code on the highest privilege degree out there within the Home windows working system: the SYSTEM account. Resulting from improper entry restrictions to this kernel element, any processes can talk with it and leverage its code injection functionality to focus on any non-protected processes.

We reported this driver to Microsoft on March 18^th, 2024 and adopted their coordinated vulnerability disclosure course of. Microsoft Safety Response Middle (MSRC) decided that that is now not a vulnerability because the offending driver was faraway from the Home windows Server Catalog on Could 1^st, 2024. ESET applied sciences detect this risk as Win64/HotPage.A and Win64/HotPage.B.

Who’s 湖北盾网网络科技有限公司 ?

Throughout its execution, the HotPage malware installs a driver, however earlier than diving into the technical particulars of its inside workings, we wished to study extra concerning the code-signing signature of this driver. What first caught our consideration was the signing certificates’s proprietor, as illustrated in Determine 1.

Because the 64-bit model of Home windows 7, kernel-mode drivers have been required to be signed to be loaded by the working system. As beforehand detailed by Mandiant Intelligence, SentinelLabs, and G DATA groups, the signing course of is constructed on belief however there have been instances the place this was abused. Plainly the Chinese language firm went by way of Microsoft’s driver code-signing necessities and managed to acquire an Prolonged Verification (EV) certificates as proven in Determine 2.

With a view to retrieve the corporate identify related to this signature, the extraction of the signers’ attributes was vital. Determine 3 reveals the SpcSpOpusInfo attribute recognized by the thing ID 1.3.6.1.4.1.311.2.1.12.

Utilizing the LIEF binary parser, it’s doable to extract the construction member programName that identifies the corporate behind this signature, as displayed in Determine 4.

We discovered a reference to this firm within the Home windows Server Catalog, as proven in Determine 5. The corporate used numerous product classes when submitting its drivers for certification. Based mostly on its identify, it seems the corporate developed two community filtering packages: a netfilter element and the HotPage driver referred as adsafe or by its inner identify KNewTalbeBase (Observe the [Tt]albe typo, which additionally happens elsewhere within the HotPage code).

Investigating the corporate by way of search engines like google didn’t yield many outcomes. In line with the corporate register dingtalk, we found that the corporate was created on January 6^th, 2022 and supplied the e-mail tackle dwadsafe@mail[.]io. The enterprise scope contains: technology-related actions comparable to improvement, providers, consulting, and so forth., but in addition promoting actions. As translated in Determine 6, the principal shareholder is now Wuhan Yishun Baishun Tradition Media Co., Ltd, a really small firm that appears to be specialised in promoting and advertising.

From the Mental Property tab, we realized that in April and Could 2022 the corporate utilized for the commerce identify Defend Web Café Safety Protection and the web site dwadsafe[.]com was created on February 22^nd, 2022. The area now resolves to localhost (127.0.0.1) and is due to this fact inaccessible. Nonetheless, a screenshot of the web site was taken on November 10^th, 2023 by a internet crawler, as seen in Determine 7.

The HTTP physique of the URL https://www.dwadsafe[.]com/login/reg.html (SHA-1: 744FFC3D8ECE37898A0559B62CC9F814006A1218) was additionally captured by VirusTotal. The supply code incorporates the outline 网吧主动防御云平台 (machine translation: Web café lively protection cloud platform). This web page features a license settlement that particulars the aim of the software program, albeit with contradictions. Desk 1 lists some attention-grabbing bits of that data.

Desk 1. Translation of the related elements of the license settlement

In line with the license settlement, the software program is certainly marketed as a safety answer for web cafés to dam advertisements. Nonetheless, regardless of the corporate’s claims that DwAdsafe doesn’t have any interception functionality, our investigation revealed that the software program does have a reasonably intrusive one and comes with pre-written, unmodifiable guidelines.

Aside from these bits of data, the corporate behind this malicious element stays a thriller.

HotPage evaluation

On this part we describe how the totally different parts are put in and work together with one another to attain their goal: injecting advertisements into the browser. Up to now, we haven’t came upon how the malware was distributed however we consider, with low confidence, that it may need been bundled with one other software program package deal or marketed as a safety product because of the degree of privileges wanted to put in the driving force. Just a few references promoting the product have been present in some boards in 2022; an instance is seen in Determine 8.

The installer drops the driving force on disk and begins a service to execute it. It decrypts its configuration file, which incorporates a listing of goal Chromium-based browsers and libraries. If such executables are discovered operating or being loaded, the driving force tries to inject one of many listed libraries into the browser course of. After hooking network-based Home windows API features, the injected library checks the URL being accessed and below sure situations, it shows one other web page to the consumer by way of numerous means.

The installer

The installer we analyzed (SHA-1: 941F0D2D4589FB8ADF224C8969F74633267B2561) is a UPX-compressed file that was uploaded to VirusTotal on 2023-08-26. Determine 9 offers a high-level overview of the driving force set up.

The installer incorporates the encrypted variations (single-byte XOR operation with the important thing 0xE3) of the driving force element, the libraries that will likely be injected into internet browser processes, and three JSON-formatted configuration recordsdata:

• chromedll incorporates the names of the focused browser libraries to hook and the focused features’ sample for hooking them,
• hotPage (unused) incorporates the record of focused browsers, allowlists of command line parameters and web sites, and the homepage URL that might be used, and
• newtalbe incorporates filtering guidelines, an API endpoint to ship primary details about the compromised pc, and one other one to handle configuration updates.

The malware begins by executing the CPUID instruction (see Hypervisor Discovery), to examine whether or not it’s operating inside a virtualized atmosphere. Then it checks if the driving force’s gadget filename .KNewTableBaseIo exists and if not, it decrypts the driving force and shops it in C:WindowsShieldNetWorkBusiness. Its identify is a randomly generated 7-character string adopted by the .sys extension. A service is created with the file path of the saved driver, and the random string is used because the service identify. Because the begin sort is ready to SERVICE_DEMAND_START, the service must be explicitly began with a purpose to load the driving force. Oddly, this adware doesn’t implement any persistence mechanisms, or no less than not on this model.

The installer proceeds to speak with and configure the driving force through its gadget filename utilizing I/O management codes within the following order:

1. 0x9C4013FC – ship the 32-bit hooking library that will likely be injected into goal internet browser processes.
2. 0x9C400FFC – ship the 64-bit hooking library that will likely be injected into goal internet browser processes.
3. 0x9C40173C – ship the chromedll configuration.

The installer retrieves the registry key related to the created service and checks to see if the values IP and port are current. These values are by no means set by this code so they’re presumably created by one other element. With out going into the main points of the community protocol, the distant server ought to serve an replace of the newtalbe configuration. The communication is encrypted with RC4, utilizing a key derived from the string ID:f~WdH+Okay?KD)r*sD4mk utilizing the Home windows BCryptGenerateSymmetricKey operate. Determine 10 reveals the content material of the configuration file.

Desk 2 describes the vital values used from this file, listed within the order that they seem within the configuration file (Determine 10).

Desk 2. newtalbe configuration description

Utilizing the hostapi URL worth of this file, an HTTP GET request is remodeled TLS with a generic Person-Agent string. The obtained knowledge is decrypted utilizing RC4 with the hostapikey worth; it incorporates a dictionary of gaming-related hostnames with their corresponding resolved tackle.

As soon as these updates are achieved, the installer sends the up to date newtalbe configuration to the driving force by issuing an I/O request with the management code 0x9C400BFC.

Lastly, the malware iterates over the record of endpoints supplied by the JSON ingredient apiurl and for every certainly one of them it creates a JSON-formatted string containing details about the compromised pc, encrypts it with RC4 utilizing the important thing Abc123!@#&XM derived through the Home windows API BcryptGenerateSymmetricKey, and sends the collected data to the distant server through an HTTP POST request. The collected data contains the pc identify, the community interface MAC tackle, the model of the working system, and the scale of the display.

Injector driver

The driving force’s fundamental goal is to inject libraries into browser purposes and alter their execution movement to alter the URL being accessed or open a web page in a brand new tab. Two threads are created to deal with requests for opening a brand new tab and injecting libraries utilizing the publicly out there Blackbone venture. Moreover, course of creation and picture loading notification routines are set to observe newly created processes and executable photos being loaded. The simplified logic of the driving force is illustrated in Determine 11.

For an unknown cause, the driving force begins by deleting its picture from the disk. Afterwards it creates a tool object named .KNewTableBaseIo and units its IRP_MJ_DEVICE_CONTROL routine to deal with the assorted I/O requests listed in Desk 3. The management codes (IOCTL) used for configuration or setting the injected libraries can solely be referred to as as soon as; due to this fact the settings can’t be up to date. These particular management codes are protected by checking that the caller’s file path matches the common expression *ShieldNetWorkEnterpriseDwBusiness_*.

Desk 3. Record of obtainable IOCTLs and their description

When dealing with the management codes 0x9C400BFC and 0x9C40173C, the driving force iterates over the loaded modules of all of the operating processes. If one of many focused modules listed within the chromedll configuration is discovered, a request to inject a library into that course of is queued.

Lastly, the driving force ends its initialization by creating two threads and setting the notification routines talked about above.

You will need to observe that the hotPage configuration is rarely set. Any mentions of this file are solely made to explain how it could be used in response to the driving force’s management movement. Basically the hotPage configuration is used to redirect the consumer to a particular web page (or homepage) stuffed with advertisements when a focused browser is launched.

The model of the software program we analyzed relied solely on the chromedll and newtalbe configurations to attain its advert injection.

Library injection thread

This thread checks the queued injection requests, and for every of them, it attaches itself to the focused course of through KeStackAttachProcess, allocates chunks of reminiscence, and copies its shellcode. Utilizing the Blackbone library operate ZwCreateThreadEx, the driving force calls the shellcode, which implements its personal PE loader and calls the entry level of the injected library.

New tab thread

The second thread makes use of the identical logic; nonetheless, the injected shellcode is totally different. It calls the Home windows API operate CreateProcessW with the command line parameter being the method identify of the focused course of concatenated with the URL that needs to be opened. The latter is manufactured from the URL adopted by the sum of the idindex and the userid variables from the hotPage configuration. As an example, the configuration proven in Determine 12 would create the string https://www.hao774[.]com/?90386-00001. Since Chromium-based browsers create a brand new course of for every new tab, making a course of from the browser course of will successfully create a brand new tab.

Determine 12 reveals the content material of the hotPage configuration file.

This configuration file incorporates the record of focused internet browsers and command line parameters that decide whether or not the method needs to be injected. The domains are both associated to gaming advertisements or web café upkeep.

Course of creation notification routine

Basically, this routine makes certain the homepage of the brand new internet browser occasion is redirected to a particular URL current within the hotPage configuration. This part describes how the driving force implements this characteristic even when it’s not used, since this model of the installer by no means sends this configuration to the driving force.

Relying on the next situations, the net browser course of will likely be marked as eligible for opening the URL within the hotPage configuration:

• that is the primary occasion of the browser and never a brand new tab being opened,
• the method’s file path matches one of many common expressions within the browser record within the hotPage configuration,
• the command line of the method doesn’t match any common expression within the wlist record of the hotPage configuration, and
• if the method’s command line contains its personal file path, it should not match any common expressions within the ppwlist record of the hotPage configuration.

As detailed within the subsequent part, when the browser course of begins loading the primary executable photos, a request to open a brand new tab is queued. Determine 13 and Determine 14, respectively, present the distinction between the professional internet listing 2345[.]com and the ad-riddled web page exhibited to the consumer.

Picture loading notification routine

This routine primarily handles two kinds of situations. If the picture being loaded is within the chromedll record, an APC routine is queued that can load one of many hooking libraries through its personal PE loader.

In any other case, if the method was marked eligible for opening a brand new web page, the malware achieves this both by opening it in a brand new tab or within the present one. If the method filename matches one of many common expressions within the browser1 record of the hotPage configuration, a request to open a brand new tab is queued and will likely be dealt with by the suitable thread (observe that the browser1 record ingredient was not current within the configuration file we retrieved). Within the different case, the web page will likely be opened within the tab being created by queuing a piece merchandise (through IoQueueWorkItemEx) that can modify the command line of the method being created. The latter attaches itself to the method, finds the export tackle of GetCommandLineA and GetCommandlineW contained in the kernelbase.dll library, and modifies the Unicode string saved in BaseAnsiCommandLine. The command line is changed with the method’s executable file path concatenated with the URL within the hotPage configuration. Determine 15 reveals a side-by-side comparability of the code answerable for discovering the command line buffer and the disassembly of the GetCommandLineA operate.

Injected library

The very first thing that the injected library does is to retrieve the hotPage and newtalbe configurations by querying the driving force. If the injected browser filename is 360Chrome, it deletes the registry key HKCUSoftware360chromeHomepage and patches the Preferences file (situated below the browser’s default listing 360chromechromeUser DataDefaultPreferences) to make the homepage level to the URL worth of the hotPage configuration.

Utilizing the Microsoft Detours hooking library, the pattern hooks SetProcessMitigationPolicy to make it return 1 with a purpose to forestall safety insurance policies from being utilized to the method, thereby permitting code injection. Then getaddrinfo is hooked to drive the browser to resolve sure hostnames to particular IP addresses to make sure the redirection is made to the correct server in case the domains don’t exist anymore.

Hooking SSL_read and SSL_write

The malware hooks the SSL_read and SSL_write features to permit the manipulation of the browser’s decrypted TLS site visitors; it does so by looking for particular patterns contained in the loaded modules, since these features should not exported. As an example, the chromewrite dictionary contained in the chromedll configuration incorporates two kinds of patterns, sslcode and oldchrome, as seen in Determine 16. They’re, respectively, used for locating newer and older variations of the DoPayloadWrite operate. We examined and confirmed that the patterns match the Microsoft Edge library msedge.dll model 122.0.2365.80.

The mode worth is used to find out the model of the sample, both 32-bit or 64-bit; the code worth is the precise byte sample, and the offset is the space from the beginning of the sample to the pointer to the SSL_write operate (see Determine 17).

As soon as SSL_write and SSL_read are discovered, they’re hooked utilizing the Detours library. For the previous, the malware inspects the info after which calls the unique operate, which encrypts and sends it. As for the latter, the injected library does the other with a purpose to manipulate decrypted knowledge. For each features, the info is inspected by the code that respectively handles the AFD_SEND and AFD_RECV management codes within the operate hooking NtDeviceIoControlFile.

Hooking NtDeviceIoControlFile and inspecting incoming and outgoing knowledge

The malicious library hooks the NtDeviceIoControlFile operate to deal with particular IOCTL codes as seen in Determine 18.

For the management code 0x12023 (AFD_SEND_DATAGRAM used when sending UDP packets), the malware cancels any DNS requests by returning STATUS_INVALID_PARAMETER if the distant port quantity is 53. This ensures that the net browser solely makes use of the hosts supplied by the newtalbe configuration.

The routine that handles the management code 0x1201F (AFD_SEND) begins by extracting the URL and the Referrer header from the request. Based mostly on the URL matching sure values within the newtalbe and hotPage configurations, the malware performs assorted actions, as described in Desk 4. In some instances, the request is shipped however the response is modified within the routine dealing with the AFD_RECV management code by totally different redirection strategies defined afterwards.

Desk 4. Record of actions carried out below sure situations when sending HTTP requests

For management code 0x12017 (AFD_RECV), the malware first retrieves the info obtained by the consumer and checks if the response was marked eligible for redirection. There are 4 kinds of redirections as described in Desk 5. The xxx string within the modified response is modified for the URL within the newtalbe configuration.

Desk 5. Redirection strategies

Determine 19 illustrates redirection technique 0 being utilized after navigating to a URL matching one of many blist URL patterns of the newtalbe configuration (www.5zy[.]cn). One other tab is opened and factors to the url laid out in the identical configuration.

Safety points and privilege escalation

When initializing its gadget object, the driving force doesn’t specify any entry management lists (ACLs) to limit who can talk with it; due to this fact, anybody can ship I/O requests to it. As talked about beforehand, some I/O management codes require the requesting course of to be in a path matching the regex:

*ShieldNetWorkEnterpriseDwBusiness_*

That is clearly not adequate to examine whether or not the speaking course of is without doubt one of the HotPage parts and may simply be bypassed by creating the required directories below a user-writable folder.

We got here up with two situations that will enable a consumer with the HotPage driver operating on their system to run code because the NT AUTHORITYSystem account. We created a proof-of-concept (PoC) script in Python to attain each situations.

State of affairs #1: Privilege escalation through arbitrary DLL injection in arbitrary processes

On this first situation, we assume that the driving force was loaded however that the chromedll configuration and the libraries to inject it weren’t set. In that case, it’s doable to create and set our personal library to inject. We created a small library that will merely log the PID of the injected course of, whether or not it’s operating with administrator privileges, and the injected course of’s file path.

As seen within the screenshot of the log file in Determine 20, quite a lot of processes have been injected with our library together with processes with administrator privileges.

It needs to be famous, nonetheless, that protected processes can’t be injected utilizing this method.

State of affairs #2: Privilege escalation through altering the command line of newly created processes

Within the first situation, we relied on the truth that each the injected libraries and the chromedll configuration weren’t set, however, as seen within the installer evaluation, they’re each set as quickly as the driving force is initially loaded. Nonetheless, the hotPage configuration by no means will get set. Based mostly on the management movement evaluation, we devised a technique to leverage the driving force’s course of creation and picture loading notification routines’ logic to execute the identical executable once more however with a special command line.

Beneath sure situations, as defined within the Course of creation notification routine and Picture loading notification routine sections, the driving force can open a brand new tab pointing to the URL current within the hotPage configuration. That is achieved both by changing the command line of the newly created browser course of or by duplicating the browser course of and altering its command line to the URL within the hotPage configuration. If we specify which course of may be duplicated and the brand new command line, we will obtain privilege escalation by concentrating on a course of with SYSTEM privileges, for example.

Conclusion

The evaluation of this reasonably generic-looking piece of malware has confirmed, as soon as once more, that adware builders are nonetheless keen to go the additional mile to attain their targets. Not solely that, these have developed a kernel element with a big set of strategies to govern processes, however in addition they went by way of the necessities imposed by Microsoft to acquire a code-signing certificates for his or her driver element.

The HotPage driver reminds us that abusing Prolonged Verification certificates remains to be a factor. As quite a lot of safety fashions are sooner or later based mostly on belief; risk actors are inclined to play alongside the road between professional and shady. Whether or not such software program is marketed as a safety answer or just bundled with different software program, the capabilities granted because of this belief expose customers to safety dangers.

As annoying as adware may be, the vulnerabilities launched by this malware go away the system open to much more harmful threats. An attacker with a non-privileged account might leverage the susceptible driver to acquire SYSTEM privileges or inject libraries into distant processes to trigger additional harm, all whereas utilizing a professional and signed driver.

ESET applied sciences detect this risk – which Microsoft faraway from the Home windows Server Catalog on Could 1^st, 2024 – as Win64/HotPage.A and Win64/HotPage.B.

For any inquiries about our analysis printed on WeLiveSecurity, please contact us at threatintel@eset.com

ESET Analysis affords personal APT intelligence stories and knowledge feeds. For any inquiries about this service, go to the ESET Risk Intelligence web page.

IoCs

A complete record of IoCs and samples may be present in our GitHub repository.

Information

Community

MITRE ATT&CK strategies

This desk was constructed utilizing model 15 of the MITRE ATT&CK framework.