Pierluigi Paganini November 27, 2021

Threat actors are targeting IKEA employees in an internal phishing campaign leveraging stolen reply-chain emails.

According to BleepingComputer, threat actors are targeting IKEA employees in phishing attacks using stolen reply-chain emails.

Once compromised the mail servers, threat actors use the access to reply to the company’s internal emails in reply-chain attacks. Sending the messages from the organizations allows the attackers to bypass detection. Threat actors also exploit the access to internal emails to target business partners.

“In internal emails seen by BleepingComputer, IKEA is warning employees of an ongoing reply-chain phishing cyber-attack targeting internal mailboxes. These emails are also being sent from other compromised IKEA organizations and business partners.” reports BleepingComputer.

“There is an ongoing cyber-attack that is targeting Inter IKEA mailboxes. Other IKEA organisations, suppliers, and business partners are compromised by the same attack and are further spreading malicious emails to persons in Inter IKEA,” reads the emails sent by IKEA to its employees. “This means that the attack can come via email from someone that you work with, from any external organisation, and as a reply to an already ongoing conversations. It is therefore difficult to detect, for which we ask you to be extra cautious.”

The above message warns employees and explains that the fraudulent messages are difficult to distinguish because have an internal source. The download links contained in the phishing messages have seven digits at the end, the company support desk told employees to report any suspicious message. The company also shared an example of a phishing email sent to its employees.

A good practice consists of contacting the sender over a different channel (i.e. Microsoft Teams chat, phone) in order to inform him of the fraudulent message.

The multinational conglomerate also disabled the possibility for its employees to release emails from quarantine, to avoid that employees can believe that the messages were isolated for error by the email filters.

Recently Trend Micro spotted a malware campaign aimed at Microsoft Exchange servers that exploits ProxyShell and ProxyLogon issues and uses stolen internal reply-chain emails to avoid detection.

The attacks were orchestrated by Squirrelwaffle, a threat actor known for sending malicious spam as replies to existing email chains. The investigation into three incidents revealed that attackers used exploits for CVE-2021-26855 (ProxyLogon), CVE-2021-34473, and CVE-2021-34523 (ProxyShell).

Once compromised the Exchange servers, threat actors use the access to reply to the company’s internal emails in reply-chain attacks containing links to weaponized documents.

“In the same intrusion, we analyzed the email headers for the received malicious emails, the mail path was internal (between the three internal exchange servers’ mailboxes), indicating that the emails did not originate from an external sender, open mail relay, or any message transfer agent (MTA).” reads the analysis published by Trend Micro. “Delivering the malicious spam using this technique to reach all the internal domain users will decrease the possibility of detecting or stopping the attack, as the mail getaways will not be able to filter or quarantine any of these internal emails.”

The emails originate from the same internal network, appear to be a continuation of a previous discussion between two employees. The attacker did not use tools for lateral movement or execute malware on the Exchange servers to avoid detection.

The emails use weaponized Office documents or include a link to them. Upon enabling the content, malicious macros are executing to download and install the malware, such as Qbot, Cobalt Strike, and SquirrelWaffle.

The excel sheets used in this campaign contain malicious Excel 4.0 macros used to download and execute the malicious DLL.

Experts recommend securing their Microsoft Exchange servers by installing security updates published by Microsoft.

BleepingComputer researchers were able to verify the download links included in the phishing messages. The links poin to a zip archive called ‘charts.zip’ that contains a weaponized Excel document. Upon opening the file and enabling the macros the infection chain will start.

The final payload installed as part of the attack is the Qbot trojan, but similar campaigns also deployed Emotet. Both malware were involved in attacks to gain access to target networks and deploy a ransomware strain.

Follow me on Twitter: @securityaffairs and Facebook

Pierluigi Paganini

(SecurityAffairs – hacking, IKEA)

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