Signal, WhatsApp, Telegram and Threema are among the most widely used messaging platforms globally, each promoting strong privacy and security features. As digital communication becomes increasingly central to personal, professional and political life, users are rightly concerned about which services offer the strongest protection against surveillance, data breaches and sophisticated cyber threats. Recent events have brought these concerns into sharp focus, particularly following reports of targeted phishing campaigns against high-profile users on Signal.
In January 2026, German authorities began investigating a wave of phishing attacks targeting journalists, activists, politicians and military personnel via the Signal messaging app. The Federal Public Prosecutor General (Bundesanwaltschaft) took over the investigation in mid-February after initial warnings from Germany’s Federal Office for the Protection of the Constitution (BfV) and the Federal Office for Information Security (BSI). By April 2026, officials confirmed the campaign remained active and was likely conducted by a state-backed cyber actor, with attempts to compromise accounts through deceptive messages designed to steal login credentials or install malware.
Despite these incidents, security experts emphasize that the vulnerabilities exploited in such attacks typically lie not in Signal’s underlying encryption protocol, but in human factors such as social engineering. The app continues to use the open-source Signal Protocol, which provides end-to-end encryption by default for all messages, voice calls and video chats. This protocol is likewise adopted by WhatsApp, though differences in metadata handling and data sharing practices distinguish the two services.
How the Four Major Messengers Compare on Security and Privacy
When evaluating the security of messaging platforms, experts consider several key factors: whether end-to-end encryption is enabled by default, how much metadata is collected, whether the code is open source for independent auditing, and what data, if any, is shared with parent companies or third parties.
Signal, operated by the nonprofit Signal Foundation, collects minimal user data — primarily just the phone number used for registration and the last date of connection. It does not store message content, contacts or location data on its servers. Its code is fully open source, allowing cryptographers and security researchers worldwide to verify its integrity. These characteristics have made Signal a preferred choice among journalists, activists and security-conscious users who prioritize confidentiality.
WhatsApp, owned by Meta (formerly Facebook), also implements the Signal Protocol for end-to-end encryption of messages, calls and media. However, while message content remains private, WhatsApp collects significantly more metadata, including user contacts, usage patterns, device information and approximate location. This data may be shared across Meta’s family of apps and used for product improvement and targeted advertising, although Meta states it does not access the content of encrypted messages.
Telegram offers optional end-to-end encryption only in its “Secret Chats” feature, which must be manually activated and does not support group chats or cloud synchronization. Regular chats on Telegram are encrypted between the user’s device and Telegram’s servers, but not end-to-end, meaning Telegram could theoretically access message content. The platform stores user data, including contacts and message history (unless in Secret Chats), on its cloud servers to enable cross-device sync. Telegram’s code is partially open source, but its server-side code remains proprietary.
Threema, a Swiss-based service, emphasizes privacy by design. It does not require a phone number or email for registration; instead, users generate a random Threema ID. End-to-end encryption is applied by default to all messages, group chats, calls and file transfers. Threema collects minimal metadata and stores no user data on its servers beyond what is necessary for message delivery. Its code is partially open source, with client applications available for public inspection, though server components are not. Threema is a paid app, which its developers say helps avoid reliance on data monetization.
Understanding the Signal Phishing Campaign
The phishing attempts observed in early 2026 did not exploit a flaw in Signal’s encryption. Instead, attackers used deceptive messages that appeared to reach from trusted contacts or official sources, tricking users into revealing their registration codes or downloading malicious software. Once compromised, an attacker could potentially access the victim’s contact list, message history and active sessions — though not past messages if the device had not been backed up or if disappearing messages were enabled.
German authorities advised users to enable Signal’s registration lock feature, which requires a PIN to re-register a phone number, and to verify safety numbers when contacting new or unfamiliar contacts. The BfV and BSI reiterated that while the Signal Protocol remains secure, users must remain vigilant against social engineering tactics that exploit trust rather than technical weaknesses.
These events underscore a broader reality in digital security: even the most robust encryption can be circumvented if users are tricked into compromising their own accounts. As one cybersecurity advisor from the BSI noted in a public briefing, “The strength of the lock matters little if the key is handed over willingly.”
Practical Steps for Safer Messaging
Users seeking to maximize their security on any platform should consider several verified practices. First, enable all available security features: for Signal, this includes activation lock, screen security and disappearing messages. On WhatsApp, users can turn on two-step verification and disable cloud backups if they wish to avoid storing encrypted data with third-party providers like Google or Apple. Telegram users should limit sensitive conversations to Secret Chats and verify the authenticity of contacts before sharing information. Threema users benefit from its default settings but should still verify contact identities using QR codes or fingerprint scanning when meeting in person.
Second, keep apps and operating systems updated to protect against known vulnerabilities that could be exploited to install spyware or malware. Third, be cautious of unsolicited messages containing links or requests for login codes, even if they appear to come from known contacts — compromise of a friend’s account could be used to launch further attacks.
Finally, consider the jurisdiction under which a service operates. Signal and Threema are based in entities with strong privacy protections (the U.S. And Switzerland, respectively), though both comply with legal requests for the limited data they retain. WhatsApp, as part of Meta, is subject to U.S. Law and has faced scrutiny over data sharing practices. Telegram, while incorporated in multiple jurisdictions, has faced criticism for its handling of illegal content and limited cooperation with law enforcement in some cases.
What This Means for Users
For most individuals, the choice of messenger involves balancing security, convenience and social connectivity. Signal offers the strongest combination of default encryption, minimal data collection and transparency, making it ideal for those who prioritize privacy above all. WhatsApp provides broad reach and ease of use, with strong message encryption but trade-offs in metadata privacy. Telegram excels in flexibility and large-group functionality but falls short of true end-to-end encryption by default. Threema offers a high level of privacy and anonymity at a cost, appealing to users who want to avoid phone number linkage and data harvesting.
No platform is immune to user-targeted attacks like phishing, but understanding how each service handles encryption and data can help users craft informed decisions. Official advisories from Germany’s BSI and BfV, as well as guidance from the Electronic Frontier Foundation and Access Now, continue to recommend Signal for high-risk users while emphasizing that security ultimately depends on both technology and user behavior.
As of April 2026, the investigation into the Signal phishing campaign remains ongoing, with no public attribution of responsibility to a specific state actor completed. Users are encouraged to consult official sources such as the BSI’s website and the Signal Foundation’s security blog for updates and technical guidance.
Stay informed, stay cautious and choose the tools that best align with your privacy needs. Share your experiences with secure messaging in the comments below, and help others navigate the evolving landscape of digital communication safety.