SpyNote is one of the most notorious Android malware families in recent years. Initially surfacing in 2020, SpyNote has evolved into a sophisticated Remote Access Trojan (RAT) that grants threat actors full control over compromised devices. In this post, we detail the origin, infection vectors, payload activities, and technical underpinnings of SpyNote. We also provide low-level analysis details for reverse engineers, including code snippets, IOC indicators, example YARA rules, and recommended mitigations.
SpyNote is an Android RAT known for its ability to exfiltrate sensitive data, spy on user activity, and maintain persistence even in adverse conditions. By disguising itself as a legitimate application—often mimicking popular antivirus or utility apps—SpyNote deceives users into granting a wide range of permissions, thereby unlocking its full potential for surveillance and control.
Originally observed in 2020, SpyNote emerged as a simple yet effective RAT. Over time, its codebase evolved, incorporating sophisticated obfuscation techniques and anti-analysis measures to thwart reverse engineering efforts. The leak of parts of its source code (e.g. variants like CypherRat) accelerated the proliferation of customized versions on underground forums and Telegram channels, enabling multiple threat actors to deploy tailored attacks against Android devices.
Source: oai_citation_attribution:0‡cyfirma.com
SpyNote’s infection vectors include:
Once installed, SpyNote leverages Android’s permission model by abusing the Accessibility Service to automate the granting of additional permissions, ensuring that critical operations can proceed without user intervention.
Source: oai_citation_attribution:1‡nortonlifelock.com
After infection, SpyNote performs a series of malicious actions:
BOOT_COMPLETED broadcast) to survive reboots and removal
attempts.Source: oai_citation_attribution:2‡bczyz1.github.io
Although attribution in malware campaigns is always challenging, analysis of SpyNote samples and their distribution channels suggests involvement from organized cybercrime groups. Some variants have been linked to threat actors operating out of Eastern Europe and South Asia, while other samples exhibit characteristics (e.g., repackaging techniques and C2 configurations) that hint at state-sponsored origins.
Source: oai_citation_attribution:3‡cryptogennepal.com
Reverse engineering SpyNote reveals several low-level techniques: -
Dynamic Loading of Dex Files: SpyNote often splits its
code into multiple dex files. The primary APK contains an obfuscated
AndroidManifest.xml that triggers the loading of secondary dex files via
reflection and MultiDex support. - GZIP Compression:
Data exfiltration is performed by compressing harvested information
(e.g., via the GZIPOutputStream API) before sending it to
the C2 server. - Network Beaconing: The malware
periodically sends compressed beacons to its C2 server using
non-standard ports, making detection by conventional IDS/IPS systems
more challenging. - Anti-Analysis Measures: It checks
for emulator signatures, debuggers, and virtual environments to avoid
detection during dynamic analysis.
Below are a few illustrative code snippets that highlight SpyNote’s techniques:
// Pseudocode to simulate user gesture via Accessibility Service
public void autoGrantPermissions() {
AccessibilityService service = getAccessibilityService();
AccessibilityEvent event = AccessibilityEvent.obtain(AccessibilityEvent.TYPE_VIEW_CLICKED);
// Simulate a click event to approve permission prompt
service.sendAccessibilityEvent(event);
}Example 2: Data Collection and Compression Before Exfiltration
// Pseudocode for collecting data and compressing it before transmission
public void collectAndSendData() {
String sms = readSMS();
String callLogs = getCallLogs();
String contacts = getContacts();
String data = sms + "\n" + callLogs + "\n" + contacts;
// Compress data using GZIP
byte[] compressedData = compressData(data.getBytes(StandardCharsets.UTF_8));
// Send compressed data to the C2 server
sendDataToC2(compressedData);
}Example 3: YARA Rule for Detecting SpyNote
rule SpyNote_Detection {
strings:
$pkg_name = "com.covidtz.suffix" fullword
$beacon = {35 00 70 6F 69 6E 67} // Example beacon pattern from network traffic
condition:
any of ($pkg_name, $beacon)
}Common IOCs for SpyNote include:
Mitigations and Recommendations
To defend against SpyNote and similar Android malware, consider the following measures:
SpyNote exemplifies the dangerous evolution of Android malware, combining traditional RAT capabilities with advanced evasion techniques and dynamic code loading. By abusing system APIs, automating permission grants, and exfiltrating a wide array of sensitive data, SpyNote poses a significant threat to both individual users and enterprises. Effective defense requires a combination of user awareness, rigorous app vetting, and sophisticated detection mechanisms—including custom YARA rules and real-time behavioral monitoring.
For reverse engineers and security analysts, understanding the low-level details of SpyNote—from its multi-dex loading and data compression methods to its network beaconing patterns—is essential for crafting effective countermeasures and improving overall mobile security.