MS Exchange Server Flaws Exploited to Deploy Keylogger in Targeted Attacks

An unknown threat actor is exploiting known security flaws in Microsoft Exchange Server to deploy a keylogger malware in attacks targeting entities in Africa and the Middle East. Russian cybersecurity firm Positive Technologies said it identified over 30 victims spanning government agencies, banks, IT companies, and educational institutions. The first-ever compromise dates back to 2021. "This

Turla's New DeliveryCheck Backdoor Breaches Ukrainian Defense Sector

The defense sector in Ukraine and Eastern Europe has been targeted by a novel .NET-based backdoor called DeliveryCheck (aka CAPIBAR or GAMEDAY) that's capable of delivering next-stage payloads. The Microsoft threat intelligence team, in collaboration with the Computer Emergency Response Team of Ukraine (CERT-UA), attributed the attacks to a Russian nation-state actor known as Turla, which is

State-Backed Hackers Employ Advanced Methods to Target Middle Eastern and African Governments

Governmental entities in the Middle East and Africa have been at the receiving end of sustained cyber-espionage attacks that leverage never-before-seen and rare credential theft and Exchange email exfiltration techniques. "The main goal of the attacks was to obtain highly confidential and sensitive information, specifically related to politicians, military activities, and ministries of foreign

New PowerExchange Backdoor Used in Iranian Cyber Attack on UAE Government

An unnamed government entity associated with the United Arab Emirates (U.A.E.) was targeted by a likely Iranian threat actor to breach the victim's Microsoft Exchange Server with a "simple yet effective" backdoor dubbed PowerExchange. According to a new report from Fortinet FortiGuard Labs, the intrusion relied on email phishing as an initial access pathway, leading to the execution of a .NET

Microsoft Urges Customers to Secure On-Premises Exchange Servers

Microsoft is urging customers to keep their Exchange servers updated as well as take steps to bolster the environment, such as enabling Windows Extended Protection and configuring certificate-based signing of PowerShell serialization payloads. "Attackers looking to exploit unpatched Exchange servers are not going to go away," the tech giant's Exchange Team said in a post. "There are too many

Iranian Government Entities Under Attack by New Wave of BackdoorDiplomacy Attacks

The threat actor known as BackdoorDiplomacy has been linked to a new wave of attacks targeting Iranian government entities between July and late December 2022. Palo Alto Networks Unit 42, which is tracking the activity under its constellation-themed moniker Playful Taurus, said it observed the government domains attempting to connect to malware infrastructure previously identified as associated

Ransomware Hackers Using New Way to Bypass MS Exchange ProxyNotShell Mitigations

Threat actors affiliated with a ransomware strain known as Play are leveraging a never-before-seen exploit chain that bypasses blocking rules for ProxyNotShell flaws in Microsoft Exchange Server to achieve remote code execution (RCE) through Outlook Web Access (OWA). "The new exploit method bypasses URL rewrite mitigations for the Autodiscover endpoint," CrowdStrike researchers Brian Pitchford,

Microsoft Issues Improved Mitigations for Unpatched Exchange Server Vulnerabilities

Microsoft on Friday disclosed it has made more improvements to the mitigation method offered as a means to prevent exploitation attempts against the newly disclosed unpatched security flaws in Exchange Server. To that end, the tech giant has revised the blocking rule in IIS Manager from ".*autodiscover\.json.*Powershell.*" to "(?=.*autodiscover\.json)(?=.*powershell)." <!--adsense--> The list of

Mitigation for Exchange Zero-Days Bypassed! Microsoft Issues New Workarounds

Microsoft has updated its mitigation measures for the newly disclosed and actively exploited zero-day flaws in Exchange Server after it was found that they could be trivially bypassed. The two vulnerabilities, tracked as CVE-2022-41040 and CVE-2022-41082, have been codenamed ProxyNotShell due to similarities to another set of flaws called ProxyShell, which the tech giant resolved last year.

ProxyNotShell – the New Proxy Hell?

Nicknamed ProxyNotShell, a new exploit used in the wild takes advantage of the recently published Microsoft Server-Side Request Forgery (SSRF) vulnerability CVE-2022-41040 and a second vulnerability, CVE-2022-41082 that allows Remote Code Execution (RCE) when PowerShell is available to unidentified attackers. Based on ProxyShell, this new zero-day abuse risk leverage a chained attack similar to

State-Sponsored Hackers Likely Exploited MS Exchange 0-Days Against ~10 Organizations

Microsoft on Friday disclosed that a single activity group in August 2022 achieved initial access and breached Exchange servers by chaining the two newly disclosed zero-day flaws in a limited set of attacks aimed at less than 10 organizations globally. "These attacks installed the Chopper web shell to facilitate hands-on-keyboard access, which the attackers used to perform Active Directory

Microsoft: Two New 0-Day Flaws in Exchange Server

Microsoft Corp. is investigating reports that attackers are exploiting two previously unknown vulnerabilities in Exchange Server, a technology many organizations rely on to send and receive email. Microsoft says it is expediting work on software patches to plug the security holes. In the meantime, it is urging a subset of Exchange customers to enable a setting that could help mitigate ongoing attacks.

In customer guidance released Thursday, Microsoft said it is investigating two reported zero-day flaws affecting Microsoft Exchange Server 2013, 2016, and 2019. CVE-2022-41040, is a Server-Side Request Forgery (SSRF) vulnerability that can enable an authenticated attacker to remotely trigger the second zero-day vulnerability — CVE-2022-41082 — which allows remote code execution (RCE) when PowerShell is accessible to the attacker.

Microsoft said Exchange Online has detections and mitigation in place to protect customers. Customers using on-premises Microsoft Exchange servers are urged to review the mitigations suggested in the security advisory, which Microsoft says should block the known attack patterns.

Vietnamese security firm GTSC on Thursday published a writeup on the two Exchange zero-day flaws, saying it first observed the attacks in early August being used to drop “webshells.” These web-based backdoors offer attackers an easy-to-use, password-protected hacking tool that can be accessed over the Internet from any browser.

“We detected webshells, mostly obfuscated, being dropped to Exchange servers,” GTSC wrote. “Using the user-agent, we detected that the attacker uses Antsword, an active Chinese-based opensource cross-platform website administration tool that supports webshell management. We suspect that these come from a Chinese attack group because the webshell codepage is 936, which is a Microsoft character encoding for simplified Chinese.”

GTSC’s advisory includes details about post-compromise activity and related malware, as well as steps it took to help customers respond to active compromises of their Exchange Server environment. But the company said it would withhold more technical details of the vulnerabilities for now.

In March 2021, hundreds of thousands of organizations worldwide had their email stolen and multiple backdoor webshells installed, all thanks to four zero-day vulnerabilities in Exchange Server.

Granted, the zero-day flaws that powered that debacle were far more critical than the two detailed this week, and there are no signs yet that exploit code has been publicly released (that will likely change soon). But part of what made last year’s Exchange Server mass hack so pervasive was that vulnerable organizations had little or no advance notice on what to look for before their Exchange Server environments were completely owned by multiple attackers.

Microsoft is quick to point out that these zero-day flaws require an attacker to have a valid username and password for an Exchange user, but this may not be such a tall order for the hackers behind these latest exploits against Exchange Server.

Steven Adair is president of Volexity, the Virginia-based cybersecurity firm that was among the first to sound the alarm about the Exchange zero-days targeted in the 2021 mass hack. Adair said GTSC’s writeup includes an Internet address used by the attackers that Volexity has tied with high confidence to a China-based hacking group that has recently been observed phishing Exchange users for their credentials.

In February 2022, Volexity warned that this same Chinese hacking group was behind the mass exploitation of a zero-day vulnerability in the Zimbra Collaboration Suite, which is a competitor to Microsoft Exchange that many enterprises use to manage email and other forms of messaging.

If your organization runs Exchange Server, please consider reviewing the Microsoft mitigations and the GTSC post-mortem on their investigations.

WARNING: New Unpatched Microsoft Exchange Zero-Day Under Active Exploitation

Security researchers are warning of previously undisclosed flaws in fully patched Microsoft Exchange servers being exploited by malicious actors in real-world attacks to achieve remote code execution on affected systems. The advisory comes from Vietnamese cybersecurity company GTSC, which discovered the shortcomings as part of its security monitoring and incident response efforts in August 2022.