Attackers Exploit Link-Wrapping Services to Steal Microsoft 365 Logins
Summary:
Between June and July 2025, the Cloudflare Email Security team identified a series of cybercriminal activity that exploited link wrapping features from security vendors Proofpoint and Intermedia. Link wrapping, a security measure designed to protect users by routing URLs through a vendor’s scanning service to block malicious content, was manipulated by the adversary to disguise their phishing payloads. While link wrapping is an effective defense against domains already known to be malicious, the attacker’s technique can actually use this to their advantage if the malicious link has not been flagged by vendors’ scanners yet. Attackers gained unauthorized access to Proofpoint-protected email accounts (i.e., accounts already employing Proofpoint URL wrapping) and used them to "launder" their malicious URLs. This technique created a seemingly trusted link, such as urldefense[.]proofpoint[.]com or url[.]emailprotection[.]link, which users were more likely to click. The campaigns leveraged multi-tiered redirects, often combining URL shorteners like Bitly (used for the initial malicious link) with the wrapped link, to increase the layers of obfuscation before leading the victim to a credential harvesting page. These phishing pages were primarily impersonating Microsoft Office 365, with lures including fake voicemail notifications, shared Teams documents, and secure document message alerts, all designed to deceive the user into relinquishing their credentials. The abuse of these trusted security services significantly increased the likelihood of a successful attack, contributing to an increase in direct financial loss.
Security Officer Comments:
The observed activity highlights a complex trend in phishing tactics, adding layers upon layers of obfuscation via redirect chains to simple malicious links by actively weaponizing legitimate security service features. The most notable aspect is the abuse of Proofpoint and Intermedia's link wrapping. By compromising a protected account, attackers can essentially integrate one of the very security measures meant to stop them into their schemes. For a recipient, seeing a urldefense or url[.]emailprotection URL effectively bypasses the cognitive red flags typically associated with suspicious links, potentially causing even experienced cybersecurity professionals to fall victim. The multi-stage infection process accomplished through multi-tiered redirects not only makes the initial malicious link harder to trace but also renders real-time detections unreliable, as they might only flag the final destination long after the initial click has occurred. The consistent use of Microsoft impersonation across these campaigns reinforces the high value of Microsoft 365 credentials, which can serve as a pivot point for further attacks and data exfiltration. The success of these campaigns is rooted in exploiting the human trust placed in familiar security tools. This trend suggests that security teams must not only focus on blocking known threats but also on quickly identifying and neutralizing any new techniques that abuse trusted services.
Suggested Corrections:
IOCs are available here.
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.bleepingcomputer.com/ne...pping-services-to-steal-microsoft-365-logins/
https://www.cloudflare.com/threat-i...a-link-wrapping-to-deliver-phishing-payloads/
Between June and July 2025, the Cloudflare Email Security team identified a series of cybercriminal activity that exploited link wrapping features from security vendors Proofpoint and Intermedia. Link wrapping, a security measure designed to protect users by routing URLs through a vendor’s scanning service to block malicious content, was manipulated by the adversary to disguise their phishing payloads. While link wrapping is an effective defense against domains already known to be malicious, the attacker’s technique can actually use this to their advantage if the malicious link has not been flagged by vendors’ scanners yet. Attackers gained unauthorized access to Proofpoint-protected email accounts (i.e., accounts already employing Proofpoint URL wrapping) and used them to "launder" their malicious URLs. This technique created a seemingly trusted link, such as urldefense[.]proofpoint[.]com or url[.]emailprotection[.]link, which users were more likely to click. The campaigns leveraged multi-tiered redirects, often combining URL shorteners like Bitly (used for the initial malicious link) with the wrapped link, to increase the layers of obfuscation before leading the victim to a credential harvesting page. These phishing pages were primarily impersonating Microsoft Office 365, with lures including fake voicemail notifications, shared Teams documents, and secure document message alerts, all designed to deceive the user into relinquishing their credentials. The abuse of these trusted security services significantly increased the likelihood of a successful attack, contributing to an increase in direct financial loss.
Security Officer Comments:
The observed activity highlights a complex trend in phishing tactics, adding layers upon layers of obfuscation via redirect chains to simple malicious links by actively weaponizing legitimate security service features. The most notable aspect is the abuse of Proofpoint and Intermedia's link wrapping. By compromising a protected account, attackers can essentially integrate one of the very security measures meant to stop them into their schemes. For a recipient, seeing a urldefense or url[.]emailprotection URL effectively bypasses the cognitive red flags typically associated with suspicious links, potentially causing even experienced cybersecurity professionals to fall victim. The multi-stage infection process accomplished through multi-tiered redirects not only makes the initial malicious link harder to trace but also renders real-time detections unreliable, as they might only flag the final destination long after the initial click has occurred. The consistent use of Microsoft impersonation across these campaigns reinforces the high value of Microsoft 365 credentials, which can serve as a pivot point for further attacks and data exfiltration. The success of these campaigns is rooted in exploiting the human trust placed in familiar security tools. This trend suggests that security teams must not only focus on blocking known threats but also on quickly identifying and neutralizing any new techniques that abuse trusted services.
Suggested Corrections:
IOCs are available here.
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.bleepingcomputer.com/ne...pping-services-to-steal-microsoft-365-logins/
https://www.cloudflare.com/threat-i...a-link-wrapping-to-deliver-phishing-payloads/