Deliver Malicious App via Other Means
Malicious applications are a common attack vector used by adversaries to gain a presence on mobile devices. This technique describes installing a malicious application on targeted mobile devices without involving an authorized app store (e.g., Google Play Store or Apple App Store). Adversaries may wish to avoid placing malicious applications in an authorized app store due to increased potential risk of detection or other reasons. However, mobile devices often are configured to allow application installation only from an authorized app store which would prevent this technique from working.
Delivery methods for the malicious application include:
- Spearphishing Attachment - Including the mobile app package as an attachment to an email message.
- Spearphishing Link - Including a link to the mobile app package within an email, text message (e.g. SMS, iMessage, Hangouts, WhatsApp, etc.), web site, QR code, or other means.
- Third-Party App Store - Installed from a third-party app store (as opposed to an authorized app store that the device implicitly trusts as part of its default behavior), which may not apply the same level of scrutiny to apps as applied by an authorized app store.
Some Android malware comes with functionality to install additional applications, either automatically or when the adversary instructs it to.
Gustuff was distributed via SMS phishing messages to numbers exfiltrated from compromised devices’ contact lists. The phishing SMS messages are sent from the compromised device to the target device.
Marcher is delivered via a link sent by SMS or email, including instructions advising the user to modify their Android device security settings to enable apps to be installed from "Unknown Sources."
RedDrop uses ads or other links within websites to encourage users to download the malicious apps using a complex content distribution network (CDN) and series of network redirects. RedDrop also downloads additional components (APKs, JAR files) from different C2 servers.
On iOS, the
iOS 9 and above requires explicit user consent before allowing installation of applications signed with enterprise distribution keys rather than installed from Apple's App Store. Users should be encouraged to not agree to installation of applications signed with enterprise distribution keys unless absolutely certain of the source of the application. On Android, the "Unknown Sources" setting must be enabled for users to install apps from sources other than an authorized app store (such as the Google Play Store), so users should be encouraged not to enable that setting.
- An EMM/MDM or mobile threat defense solution may be able to identify the presence of apps installed from sources other than an authorized app store.
- An EMM/MDM or mobile threat defense solution may be able to identify Android devices configured to allow apps to be installed from "Unknown Sources".
- Enterprise email security solutions can identify the presence of Android or iOS application packages within email messages.
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