Emulating the Stealthy StrelaStealer Malware
Summary:
StrelaStealer, first uncovered in 2022, is a sophisticated information-stealing malware designed to extract email account credentials from widely used email clients like Microsoft Outlook and Mozilla Thunderbird. It is primarily distributed through large-scale phishing campaigns, which deliver ZIP archives containing malicious JavaScript files. These scripts are designed to retrieve and execute a StrelaStealer DLL payload from a WebDAV server directly in memory, initiating the infection chain. StrelaStealer has targeted over 100 organizations across Europe and the U.S., with notable activity in Italy, Spain, Germany, and Ukraine. Recent campaigns have demonstrated evolving obfuscation, anti-analysis techniques, and varied initial access vectors—including the use of PowerShell and Regsvr32—to evade detection. Overall, StrelaStealer’s operations involve extensive reconnaissance, including system, software, and country locale discovery, followed by exfiltration of sensitive data via HTTP post requests.
Security Officer Comments:
Infostealers remain a favored tool among threat actors for harvesting sensitive information, particularly user credentials, that can serve as a foothold for gaining initial access into target environments. StrelaStealer, a notable example of such malware, has been attributed to the threat cluster HIVE-0145, a group believed to operate as a financially motivated initial access broker. Although HIVE-0145 is currently thought to be the exclusive operator of StrelaStealer, the malware’s stealthy obfuscation techniques and ability to exfiltrate credentials from email clients like Microsoft Outlook and Mozilla Thunderbird underscore its potential appeal to other threat actors. As such, StrelaStealer may be increasingly repurposed in future campaigns, broadening its impact across the threat landscape.
Suggested Corrections:
Users should always be cautious of individuals or organizations that ask for personal information. Most companies will not ask for sensitive data from their customers. If in doubt, users should verify with the company itself to avoid any potential issues.
Users should always take a close look at the sender’s display name when checking the legitimacy of an email. Most companies use a single domain for their URLs and emails, so a message that originates from a different domain is a red flag.
As a general rule, users should not click links or download files even if they come from seemingly “trustworthy” sources.
Check for mismatched URLs. While an embedded URL might seem perfectly valid, hovering above it might show a different web address. In fact, users should avoid clicking links in emails unless they are certain that it is a legitimate link.
Users should always be on the lookout for any grammatical errors and spelling mistakes. Legitimate companies will often employ proofreaders and editors who ensure that the materials they send out are error-free.
Users should not be frightened or intimidated by messages that have an alarmist tone. They should double check with the company if they are uncertain about the status of their accounts.
Phishing emails are designed to be sent to a large number of people, so they need to be as impersonal as possible. Users should check whether the message contains a generic subject and greeting, as this can be a sign of a phishing attempt.
Although not every end user has access to advanced anti-phishing software, they can still use the built-in protection of their email clients to filter messages. One example is setting the email client to block all images unless approved.
Legitimate companies will never send confirmation emails unless there are specific reasons for doing so. In fact, most companies will avoid sending unsolicited messages unless it’s for company updates, newsletters, or advertising purposes.
Users should always take the context of an email or message into account. For example, most online accounts do away with viewable member numbers, so users should be wary if they receive emails containing a “member number” for services that generally don’t use them.
It is important to take note of unusual information in the text of the message. Any mentions of operating systems and software that are not typically used by consumers can often be indicators of a phishing attempt.
If it seems suspicious, it probably is. Users should always err on the side of caution when it comes to sending out personally identifiable information through messages and emails.
Link(s):
https://www.attackiq.com/2025/04/17/emulating-strelastealer/
StrelaStealer, first uncovered in 2022, is a sophisticated information-stealing malware designed to extract email account credentials from widely used email clients like Microsoft Outlook and Mozilla Thunderbird. It is primarily distributed through large-scale phishing campaigns, which deliver ZIP archives containing malicious JavaScript files. These scripts are designed to retrieve and execute a StrelaStealer DLL payload from a WebDAV server directly in memory, initiating the infection chain. StrelaStealer has targeted over 100 organizations across Europe and the U.S., with notable activity in Italy, Spain, Germany, and Ukraine. Recent campaigns have demonstrated evolving obfuscation, anti-analysis techniques, and varied initial access vectors—including the use of PowerShell and Regsvr32—to evade detection. Overall, StrelaStealer’s operations involve extensive reconnaissance, including system, software, and country locale discovery, followed by exfiltration of sensitive data via HTTP post requests.
Security Officer Comments:
Infostealers remain a favored tool among threat actors for harvesting sensitive information, particularly user credentials, that can serve as a foothold for gaining initial access into target environments. StrelaStealer, a notable example of such malware, has been attributed to the threat cluster HIVE-0145, a group believed to operate as a financially motivated initial access broker. Although HIVE-0145 is currently thought to be the exclusive operator of StrelaStealer, the malware’s stealthy obfuscation techniques and ability to exfiltrate credentials from email clients like Microsoft Outlook and Mozilla Thunderbird underscore its potential appeal to other threat actors. As such, StrelaStealer may be increasingly repurposed in future campaigns, broadening its impact across the threat landscape.
Suggested Corrections:
Users should always be cautious of individuals or organizations that ask for personal information. Most companies will not ask for sensitive data from their customers. If in doubt, users should verify with the company itself to avoid any potential issues.
Users should always take a close look at the sender’s display name when checking the legitimacy of an email. Most companies use a single domain for their URLs and emails, so a message that originates from a different domain is a red flag.
As a general rule, users should not click links or download files even if they come from seemingly “trustworthy” sources.
Check for mismatched URLs. While an embedded URL might seem perfectly valid, hovering above it might show a different web address. In fact, users should avoid clicking links in emails unless they are certain that it is a legitimate link.
Users should always be on the lookout for any grammatical errors and spelling mistakes. Legitimate companies will often employ proofreaders and editors who ensure that the materials they send out are error-free.
Users should not be frightened or intimidated by messages that have an alarmist tone. They should double check with the company if they are uncertain about the status of their accounts.
Phishing emails are designed to be sent to a large number of people, so they need to be as impersonal as possible. Users should check whether the message contains a generic subject and greeting, as this can be a sign of a phishing attempt.
Although not every end user has access to advanced anti-phishing software, they can still use the built-in protection of their email clients to filter messages. One example is setting the email client to block all images unless approved.
Legitimate companies will never send confirmation emails unless there are specific reasons for doing so. In fact, most companies will avoid sending unsolicited messages unless it’s for company updates, newsletters, or advertising purposes.
Users should always take the context of an email or message into account. For example, most online accounts do away with viewable member numbers, so users should be wary if they receive emails containing a “member number” for services that generally don’t use them.
It is important to take note of unusual information in the text of the message. Any mentions of operating systems and software that are not typically used by consumers can often be indicators of a phishing attempt.
If it seems suspicious, it probably is. Users should always err on the side of caution when it comes to sending out personally identifiable information through messages and emails.
Link(s):
https://www.attackiq.com/2025/04/17/emulating-strelastealer/