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Microsoft Exchange servers worldwide hit by stealthy new backdoor

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Researchers have identified stealthy new malware that threat actors have been using for the past 15 months to backdoor Microsoft Exchange servers after they have been hacked.

Dubbed SessionManager, the malicious software poses as a legitimate module for Internet Information Services (IIS), the web server installed by default on Exchange servers. Organizations often deploy IIS modules to streamline specific processes on their web infrastructure. Researchers from security firm Kaspersky have identified 34 servers belonging to 24 organizations that have been infected with SessionManager since March 2021. As of earlier this month, Kaspersky said, 20 organizations remained infected.

Stealth, persistence, power

Malicious IIS modules offer an ideal means to deploy powerful, persistent, and stealthy backdoors. Once installed, they will respond to specifically crafted HTTP requests sent by the operator instructing the server to collect emails, add further malicious access, or use the compromised servers for clandestine purposes. To the untrained eye, the HTTP requests look unremarkable, even though they give the operator complete control over the machine.

“Such malicious modules usually expect seemingly legitimate but specifically crafted HTTP requests from their operators, trigger actions based on the operators’ hidden instructions if any, then transparently pass the request to the server for it to be processed just like any other request,” Kaspersky researcher Pierre Delcher wrote. “As a result, such modules are not easily spotted by usual monitoring practices: they do not necessarily initiate suspicious communications to external servers, receive commands through HTTP requests to a server that is specifically exposed to such processes, and their files are often placed in overlooked locations that contain a lot of other legitimate files.”

Kaspersky

Once SessionManager is deployed, operators use it to profile the infected environment further, gather passwords stored in memory, and install additional tools, including a PowerSploit-based reflective loader, Mimikat SSP, ProcDump, and a legitimate Avast memory dump tool. Kaspersky obtained multiple SessionManager variants that date back to at least March 2021. The samples show a steady evolution that has added more features with each new version. The most recent version of the malicious module includes the following:

Command name
(SM_SESSION cookie value)
Command parameters
(additional cookies)
Associated capability
GETFILE FILEPATH: path of file to be read. FILEPOS1: offset at which to start reading, from file start.

FILEPOS2: maximum number of bytes to read.

Read the content of a file on the compromised server and send it to the operator as an HTTP binary file named cool.rar.
PUTFILE FILEPATH: path of file to be written.

FILEPOS1: offset at which to start writing.

FILEPOS2: offset reference.

FILEMODE: requested file access type.

Write arbitrary content to a file on the compromised server. The data to be written in the specified file is passed within the HTTP request body.
DELETEFILE FILEPATH: path of file to be deleted. Delete a file on the compromised server.
FILESIZE FILEPATH: path of file to be measured. Get the size (in bytes) of the specified file.
CMD None. Run an arbitrary process on the compromised server. The process to run and its arguments are specified in the HTTP request body using the format: <executable path>t<arguments>. The standard output and error data from process execution are sent back as plain text to the operator in the HTTP response body.
PING None. Check for SessionManager deployment. The “Wokring OK” (sic.) message will be sent to the operator in the HTTP response body.
S5CONNECT S5HOST: hostname to connect to (exclusive with S5IP).

S5PORT: offset at which to start writing.

S5IP: IP address to connect to if no hostname is given (exclusive with S5HOST).

S5TIMEOUT: maximum delay in seconds to allow for connection.

Connect from compromised host to a specified network endpoint, using a created TCP socket. The integer identifier of the created and connected socket will be returned as the value of the S5ID cookie variable in the HTTP response, and the status of the connection will be reported in the HTTP response body.
S5WRITE S5ID: identifier of the socket to write to, as returned by S5CONNECT. Write data to the specified connected socket. The data to be written in the specified socket is passed within the HTTP request body.
S5READ S5ID: identifier of the socket to read from, as returned by S5CONNECT. Read data from the specified connected socket. The read data is sent back within the HTTP response body.
S5CLOSE S5ID: identifier of the socket to close, as returned by S5CONNECT. Terminate an existing socket connection. The status of the operation is returned as a message within the HTTP response body.

Remember ProxyLogon?

SessionManager gets installed after threat actors have exploited vulnerabilities known as ProxyLogon within Microsoft Exchange servers. Kaspersky has found it infecting NGOs, governments, militaries, and industrial organizations in Africa, South America, Asia, and Europe.

Kaspersky

Kaspersky said it has medium-to-high confidence that a previously identified threat actor that researchers call Gelsemium has been deploying SessionManager. Security firm ESET published a deep dive on the group (PDF) last year. Kaspersky’s attribution is based on the overlap of code used by the two groups and victims targeted.

Disinfecting servers that have been hit by SessionManager or similar malicious IIS modules is a complicated process. Kaspersky’s post contains indicators that organizations can use to determine if they’ve been infected and steps they should take in the event they’ve been infected.

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Cyberattack on Albanian government suggests new Iranian aggression

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Enlarge / Tirane, Albania.

Pawel Toczynski | Getty Images

In mid-July, a cyberattack on the Albanian government knocked out state websites and public services for hours. With Russia’s war raging in Ukraine, the Kremlin might seem like the likeliest suspect. But research published on Thursday by the threat intelligence firm Mandiant attributes the attack to Iran. And while Tehran’s espionage operations and digital meddling have shown up all over the world, Mandiant researchers say that a disruptive attack from Iran on a NATO member is a noteworthy escalation.

The digital attacks targeting Albania on July 17 came ahead of the “World Summit of Free Iran,” a conference scheduled to convene in the town of Manëz in western Albania on July 23 and 24. The summit was affiliated with the Iranian opposition group Mujahadeen-e-Khalq, or the People’s Mojahedin Organization of Iran (often abbreviated MEK, PMOI, or MKO). The conference was postponed the day before it was set to begin because of reported, unspecified “terrorist” threats.

Mandiant researchers say that attackers deployed ransomware from the Roadsweep family and may have also utilized a previously unknown backdoor, dubbed Chimneysweep, as well as a new strain of the Zeroclear wiper. Past use of similar malware, the timing of the attacks, other clues from the Roadsweep ransomware note, and activity from actors claiming responsibility for the attacks on Telegram all point to Iran, Mandiant says.

“This is an aggressive escalatory step that we have to recognize,” says John Hultquist, Mandiant’s vice president of intelligence. “Iranian espionage happens all the time all over the world. The difference here is this isn’t espionage. These are disruptive attacks, which affect the lives of everyday Albanians who live within the NATO alliance. And it was essentially a coercive attack to force the hand of the government.”

Iran has conducted aggressive hacking campaigns in the Middle East and particularly in Israel, and its state-backed hackers have penetrated and probed manufacturing, supply, and critical infrastructure organizations. In November 2021, the US and Australian governments warned that Iranian hackers were actively working to gain access to an array of networks related to transportation, health care, and public health entities, among others. “These Iranian government-sponsored APT actors can leverage this access for follow-on operations, such as data exfiltration or encryption, ransomware, and extortion,” the Department of Homeland Security’s Cybersecurity and Infrastructure Security Agency wrote at the time.

Tehran has limited how far its attacks have gone, though, largely keeping to data exfiltration and reconnaissance on the global stage. The country has, however, participated in influence operations, disinformation campaigns, and efforts to meddle in foreign elections, including targeting the US.

“We’ve become used to seeing Iran being aggressive in the Middle East where that activity just has never stopped, but outside of the Middle East they’ve been far more restrained,” Hultquist says. “I’m concerned that they may be more willing to leverage their capability outside of the region. And they clearly have no qualms about targeting NATO states, which suggests to me that whatever deterrents we believe exist between us and them may not exist at all.”

With Iran claiming that it now has the ability to produce nuclear warheads, and representatives from the country meeting with US officials in Vienna about a possible revival of the 2015 nuclear deal between the countries, any signal about Iran’s possible intentions and risk tolerance when it comes to dealing with NATO are significant.

This story originally appeared on wired.com.

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“Huge flaw” threatens US emergency alert system, DHS researcher warns

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The US Department of Homeland Security is warning of vulnerabilities in the nation’s emergency broadcast network that makes it possible for hackers to issue bogus warnings over radio and TV stations.

“We recently became aware of certain vulnerabilities in EAS encoder/decoder devices that, if not updated to most recent software versions, could allow an actor to issue EAS alerts over the host infrastructure (TV, radio, cable network),” the DHS’s Federal Emergency Management Agency (FEMA) warned. “This exploit was successfully demonstrated by Ken Pyle, a security researcher at CYBIR.com, and may be presented as a proof of concept at the upcoming DEFCON 2022 conference in Las Vegas, August 11-14.”

Pyle told reporters at CNN and Bleeping Computer that the vulnerabilities reside in the Monroe Electronics R189 One-Net DASDEC EAS, an Emergency Alert System encoder and decoder. TV and radio stations use the equipment to transmit emergency alerts. The researcher told Bleeping Computer that “multiple vulnerabilities and issues (confirmed by other researchers) haven’t been patched for several years and snowballed into a huge flaw.”

“When asked what can be done after successful exploitation, Pyle said: ‘I can easily obtain access to the credentials, certs, devices, exploit the web server, send fake alerts via crafts message, have them valid / pre-empting signals at will. I can also lock legitimate users out when I do, neutralizing or disabling a response,’” Bleeping Computer added.

This isn’t the first time federal officials have warned of vulnerabilities in the emergency alert system.

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North Korea-backed hackers have a clever way to read your Gmail

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Researchers have unearthed never-before-seen malware that hackers from North Korea have been using to surreptitiously read and download email and attachments from infected users’ Gmail and AOL accounts.

The malware, dubbed SHARPEXT by researchers from security firm Volexity, uses clever means to install a browser extension for the Chrome and Edge browsers, Volexity reported in a blog post. The extension can’t be detected by the email services, and since the browser has already been authenticated using any multifactor authentication protections in place, this increasingly popular security measure plays no role in reining in the account compromise.

The malware has been in use for “well over a year,” Volexity said, and is the work of a hacking group the company tracks as SharpTongue. The group is sponsored by North Korea’s government and overlaps with a group tracked as Kimsuky by other researchers. SHARPEXT is targeting organizations in the US, Europe, and South Korea that work on nuclear weapons and other issues North Korea deems important to its national security.

Volexity President Steven Adair said in an email that the extension gets installed “by way of spear phishing and social engineering where the victim is fooled into opening a malicious document. Previously we have seen DPRK threat actors launch spear phishing attacks where the entire objective was to get the victim to install a browser extension vs it being a post exploitation mechanism for persistence and data theft.” In its current incarnation, the malware works only on Windows, but Adair said there’s no reason it couldn’t be broadened to infect browsers running on macOS or Linux, too.

The blog post added: “Volexity’s own visibility shows the extension has been quite successful, as logs obtained by Volexity show the attacker was able to successfully steal thousands of emails from multiple victims through the malware’s deployment.”

Installing a browser extension during a phishing operation without the end-user noticing isn’t easy. SHARPEXT developers have clearly paid attention to research like what’s published here, here, and here, which shows how a security mechanism in the Chromium browser engine prevents malware from making changes to sensitive user settings. Each time a legitimate change is made, the browser takes a cryptographic hash of some of the code. At startup, the browser verifies the hashes, and if any of them don’t match, the browser requests the old settings be restored.

For attackers to work around this protection, they must first extract the following from the computer they’re compromising:

  • A copy of the resources.pak file from the browser (which contains the HMAC seed used by Chrome)
  • The user’s S-ID value
  • The original Preferences and Secure Preferences files from the user’s system

After modifying the preference files, SHARPEXT automatically loads the extension and executes a PowerShell script that enables DevTools, a setting that allows the browser to run customized code and settings.

“The script runs in an infinite loop checking for processes associated with the targeted browsers,” Volexity explained. “If any targeted browsers are found running, the script checks the title of the tab for a specific keyword (for example’ 05101190,’ or ‘Tab+’ depending on the SHARPEXT version). The specific keyword is inserted into the title by the malicious extension when an active tab changes or when a page is loaded.”

Volexity

The post continued:

The keystrokes sent are equivalent to Control+Shift+J, the shortcut to enable the DevTools panel. Lastly, the PowerShell script hides the newly opened DevTools window by using the ShowWindow() API and the SW_HIDE flag. At the end of this process, DevTools is enabled on the active tab, but the window is hidden.

In addition, this script is used to hide any windows that could alert the victim. Microsoft Edge, for example, periodically displays a warning message to the user (Figure 5) if extensions are running in developer mode. The script constantly checks if this window appears and hides it by using the ShowWindow() and the SW_HIDE flag.

Volexity

Once installed, the extension can perform the following requests:

HTTP POST Data Description
mode=list List previously collected email from the victim to ensure duplicates are not uploaded. This list is continuously updated as SHARPEXT executes.
mode=domain List email domains with which the victim has previously communicated. This list is continuously updated as SHARPEXT executes.
mode=black Collect a blacklist of email senders that should be ignored when collecting email from the victim.
mode=newD&d=[data] Add a domain to the list of all domains viewed by the victim.
mode=attach&name=[data]&idx=[data]&body=[data] Upload a new attachment to the remote server.
mode=new&mid=[data]&mbody=[data] Upload Gmail data to the remote server.
mode=attlist Commented by the attacker; receive an attachments list to be exfiltrated.
mode=new_aol&mid=[data]&mbody=[data] Upload AOL data to the remote server.

SHARPEXT allows the hackers to create lists of email addresses to ignore and to keep track of email or attachments that have already been stolen.

Volexity created the following summary of the orchestration of the various SHARPEXT components it analyzed:

Volexity

The blog post provides images, file names, and other indicators that trained people can use to determine if they have been targeted or infected by this malware. The company warned that the threat it poses has grown over time and isn’t likely to go away anytime soon.

“When Volexity first encountered SHARPEXT, it seemed to be a tool in early development containing numerous bugs, an indication the tool was immature,” the company said. “The latest updates and ongoing maintenance demonstrate the attacker is achieving its goals, finding value in continuing to refine it.”

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