Phishing has been a favored attack vector for threat actors for nearly three decades, and its utilization persists until it loses its effectiveness. The success of phishing largely hinges on exploiting the weakest link in an organization's cybersecurity chain—human behavior.

“Phishing is largely the same whether in the cloud or on-prem[ise], in that it’s exploiting human behavior more than it’s exploiting technology,” said Emily Phelps, director at Cyware.

These attacks primarily aim to pilfer credentials, granting threat actors unfettered access within an organization's infrastructure. Yet, successful cloud-based phishing assaults might be more intricate due to the nuanced ownership of the environment.

Phelps explained that in an on-premise scenario, a compromised ecosystem would be under the jurisdiction of an organization's security and IT team. However, in the cloud—like AWS or Azure—a breached environment is managed by respective organizations yet ultimately owned by Amazon or Microsoft.

As an increasing number of applications gravitate toward cloud computing, threat actors are unsurprisingly drawn to exploit this realm. Palo Alto Networks Unit 42's report unveiled a staggering 1100% surge in newly identified phishing URLs on legitimate SaaS platforms from June 2021 to June 2022.

The report delineated a tactic where visitors to legitimate web pages are enticed to click a link directing them to a credential-stealing site. By leveraging a legitimate webpage as the principal phishing site, attackers can modify the link to direct victims to a new malicious page, thereby sustaining the original campaign's efficacy.

Cloud applications provide an ideal launchpad for phishing assaults due to their ability to bypass conventional security systems. Cloud-based phishing is further facilitated by the ease of luring unsuspecting users into clicking malevolent email links. Beyond SaaS platforms, cloud applications such as video conferencing and workforce messaging are also being increasingly exploited for launching attacks.

Among the most robust defenses against credential-stealing phishing attacks is multifactor authentication (MFA). This approach incorporates several security factors, including something known (like a password), something possessed (such as a phone or email for code reception), and/or something inherent (like a fingerprint). By requiring an additional code-sharing device or a biometric tool for authentication, MFA heightens the difficulty for attackers to breach these security layers.

In the event of a user falling prey to a phishing attack and credentials being compromised, MFA introduces an additional layer of verification inaccessible to threat actors. This may involve SMS verification, email confirmation, or an authenticator app, with the latter being recommended by Phelps.

However, as MFA proves effective against credential theft, threat actors have escalated their strategies to compromise MFA credentials. Phishing remains one of their favored methods, as cautioned by the Cybersecurity and Infrastructure Security Agency (CISA):

"In a widely used phishing technique, a threat actor sends an email to a target that convinces the user to visit a threat actor-controlled website that mimics a company’s legitimate login portal. The user submits their username, password, as well as the 6-digit code from their mobile phone’s authenticator app.”

To counter this, CISA endorses phishing-resistant MFA as a strategy to enhance overall cloud security against phishing attacks. Fast ID Online/WebAuthn authentication stands out as a popular option. It operates through separate physical tokens linked to USB or NFC devices or embedded authenticators within laptops and mobile devices.

An alternative approach, albeit less common, is PKI-based phishing-resistant MFA, employing security-chip embedded smart cards linked to both an organization and the individual user. While highly secure, this method necessitates mature security and identity management systems.

While any form of MFA contributes to safeguarding cloud data against phishing, relying solely on commonly used code-sharing methods falls short. Threat actors have devised ways to manipulate users into revealing these codes, often relying on users' inconsistent MFA setup practices. Adopting phishing-resistant MFA and incorporating multiple layers of authentication offers the utmost security against this prevalent cyber threat.