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While the most common cloud apps are also the most exploited for delivering malicious content, opportunistic and state-sponsored threat actors are constantly looking for additional cloud services to leverage throughout multiple stages of the attack chain.
The growing exploitation of cloud services has led the main cloud service providers to enforce restrictive controls to mitigate the risk of possible abuse of their services. And even though a less known service means a lower chance of success for the attackers (the users could be uncomfortable with downloading or accessing content from a cloud application they are not familiar with), there are still more advantages than drawbacks: a cloud service offers simplified hosting and the corresponding malicious traffic is easily hidden among the legitimate sessions.
In a recent example, discovered by researchers at ESET while investigating the recent supply-chain attack to 3CX carried out by the infamous North Korean threat actor Lazarus Group, the same attackers deployed an unknown Linux malware disguised as a PDF document distributed via spear phishing or direct messages. The malware was distributed as part of a new campaign, considered a follow-up to Operation Dream Job, targeting people working in software or DeFi platforms with fake job offers on social media.
The first stage payload of this campaign is a downloader, dubbed OdicLoader by the researchers, that when executed displays a decoy PDF document, and then downloads a second-stage backdoor from the OpenDrive (no it is not OneDrive!) cloud storage service.
It is interesting to note that the Lazarus Group has a certain predisposition to exploit cloud services in their campaigns: even in the case of the 3CX attack, the threat actors exploited GitHub in a complex multi-stage attack chain where the trojanized 3CX client downloaded apparently innocuous icon files from GitHub, encoding the information needed to download the information stealer in the next stage of the attack: an unprecedented variant of the Dead Drop Resolver technique.
How Netskope mitigates the risk of legitimate cloud services exploited by threat actors
Although OpenDrive is maybe not one of the most common cloud storage services, it is certainly one where the Netskope Next Gen SWG can provide granular access control, threat protection, and DLP capabilities (the app connector is able to recognize the following activities: “Create”, “Delete”, “Download”, “Edit”, “Login Attempt”, “Login Failed”, “Login Successful”, “Logout”, “Share”, “Upload”, “View”, and to enforce DLP policies for the “Download” and “Upload” activities, a much deeper visibility than legacy SWGs).
The organization might decide to completely block access to the unneeded cloud storage service, or simply prevent specific, potentially dangerous activities (such as “Download” or “Upload”).
A similar policy can also be applied to GitHub, with the additional advantage that GitHub is also among the hundreds of services for which instance detection is available. So if an unknown instance of a corporate cloud service like GitHub is exploited as a command and control, dead drop resolver, or a malware distribution point, it is possible to configure a policy that prevents potentially dangerous activities just from non-corporate instances.
Netskope customers are also protected against malware distributed from a legitimate cloud service and the web in general by Netskope Threat Protection. Netskope Threat Protection scans web and cloud traffic to detect known and unknown threats with a comprehensive set of engines, including signature-based AV, machine learning-based detectors for executables and Office documents, and sandboxing, including patient zero protection.
Netskope Cloud Exchange provides powerful integration tools to leverage investments across their security posture through integration with third-party tools, such as threat intelligence feeds and endpoint detection technologies.
Finally, Netskope Advanced Analytics provides specific dashboards to assess the risk of rogue cloud instances being exploited to deliver malware or becoming the target of anomalous communications, with rich details and insights, supporting security teams in the analysis and mitigation/remediation process.