The answer to “can I read messages from another phone?” changes completely depending on who the other person is. It’s not a question of intent or the seriousness of the suspicion: it’s a question of legal ties. This guide goes through the cases one by one and explains, in each case, what is permitted and what constitutes a crime.
minor child
Allowed. Parents and guardians exercise parental authority and can supervise the use of the device.
In practice, the recommendation is to do it openly and using an official tool. Google Family Link and the Usage Time iPhone apps control screen time, approve installations, filter content, and show location — but they don't display the content of conversations because messages are end-to-end encrypted.
The older the teenager, the more the agreement is worth than the barrier: the discovery of hidden surveillance often shuts down the communication channel precisely at the age when it is most needed.
Google Family Link
AndroidChild over 18 years of age
Forbidden without consent. Parental authority ends at the age of majority. Paying the cell phone bill or data plan doesn't change that—the person who pays doesn't become the data owner.
Spouse or partner
Forbidden without consent. This is the case that generates the most doubt and the one that allows for the fewest exceptions. The Article 154-A of the Penal Code It makes no exception for affective ties, and the property regime does not affect the confidentiality of communications. The penalty is imprisonment from 1 to 4 years and a fine, increasing to 2 to 5 years when there is obtaining of the content of private communications.
Two practical points that often surprise: a cell phone without a password does not equate to authorization, and a screenshot obtained in this way tends to be discarded in the process as illicit evidence — documenting, incidentally, the conduct of the person who produced it.
Ex-partner
Forbidden, and made worse by the context. In addition to the crime of trespassing, monitoring an ex-partner can constitute stalking — the Article 147-A of the Penal Code, The law, included by Law 14.132/2021, punishes those who stalk someone by threatening their integrity or disturbing their freedom, with increased penalties when the victim is a woman. It also supports requests for protective measures.
Employee
Allowed only on corporate devices. The company monitors the device it provides, as long as the policy is communicated in writing, signed, and restricted to professional use. The employee's personal device is off-limits, even if they use it for work—and monitoring it could lead to labor and criminal exposure.
Elderly parent
It depends on legal capacity. A capable adult decides about their own device, and monitoring requires their consent. In cases of guardianship or legal incapacitation, the guardian acts within the limits defined by the court decision.
In most real-world situations—such as fear of phone scams—the best approach is a combined one: mutually agreed-upon location sharing and joint setup of call blocking.
Friend, colleague, neighbor
Prohibited. There is no legal basis for this, and curiosity is not a legal ground for anything.
Yourself
Released. Your conversations, your records, your backup. It's worth remembering what you can do without depending on anyone: link up to four devices to your account, export an entire conversation via the contact menu, restore your backup, and request a call log from your carrier.
When there is a serious reason.
If the information is truly necessary for a legal process, the lawyer should request a court order to break the confidentiality of telecommunications data. The data comes from the operator or platform with a chain of custody, which makes it usable evidence—unlike a screenshot.
And there's a deadline: the Brazilian Internet Bill of Rights establishes a minimum retention period of one year for connection logs and six months for application access logs.
Frequently Asked Questions
If I pay my cell phone bill, can I still see the messages?
No. Paying for the service does not transfer ownership of the data nor does it eliminate confidentiality.
What if the device is registered in my name?
No, not when the user is another adult. What the law protects is the person's communication, not the ownership of the object.
Can I install a monitoring app on my 17-year-old son's cell phone?
Legally, it's possible as long as he's a minor. Doing it together tends to work better, including for the purpose of protection.
Can my boss read my personal WhatsApp messages?
No. Only the corporate device, with an informed policy and limited to professional use.
I found out they're monitoring me. What do I do?
Check WhatsApp's Accessibility, Device Administrators, and Connected Devices settings. Save evidence before removing, and seek guidance — especially in the context of domestic violence. 180 The service is free of charge, and abrupt removal can escalate the risk.
In summary
Only three relationships authorize monitoring another person's device: a minor child, an adult who has freely and knowingly consented, and an employee on a corporate device with a written policy. Outside of these categories—spouse, ex-partner, adult child, friend—it constitutes unauthorized access to a computer system, punishable by imprisonment, and the evidence is inadmissible.
How to truly take advantage of it.
- Enable installation approval. It prevents new apps from appearing without your knowledge, which is half the problem.
- Use the official tool. Google Family Link on Android and Screen Time on iPhone: free, visible on the device, and without requiring you to disable any protection.
- Review the agreement every few months. Limits that don't match age become a source of conflict and challenges.
- Set a limit per application, not just a total limit. Allowing free study time and restricting short video time works better than a single limit.
Common mistakes that are costly
- Don't believe promises of monitoring based solely on a phone number; it doesn't exist.
- Relying on evidence obtained through unauthorized access in a legal proceeding—it is discarded and exposes whoever produced it.
- Disabling Play Protect to install files from outside sources is the most common vector for banking trojans.
- Installing hidden software on an adult's cell phone is a crime under article 154-A, punishable by 1 to 4 years imprisonment.
What the cell phone itself already does.
To find a lost device, Find My Device and Find My iPhone are free and come standard: they sound an alarm even when the device is on silent, show it on a map, and remotely lock and erase it. It's worth checking today if they are activated — once lost, you can't configure them anymore.
The articles that are usually cited
Those who ask if it "causes problems" rarely know how many different legal provisions can apply to the same act. It's not just one, and they are not mutually exclusive.
- Computer intrusion. The Penal Code punishes anyone who invades another person's device, whether connected to a network or not, to obtain, alter, or destroy data, as well as anyone who installs vulnerabilities to gain an advantage. The penalty increases when the obtained material is disclosed.
- Violation of correspondence and communication. Opening someone else's communication, even without hacking into their device, has its own specific legal classification.
- Persecution. Repeatedly monitoring, harassing, or controlling someone, restricting their freedom, has been a separate crime since 2021. Continuous monitoring of a former partner frequently fits this description.
- Disclosure of intimate scene. If the obtained material produced photos or videos of a sexual nature and they were subsequently shared, there is a specific and more serious type of offense.
Intercepting communications without judicial authorization is a crime under its own law. There is no such thing as authorizing something on one's own initiative simply because the other party "deserved it.".
Three different processes can arise from the same act.
This is the point that often goes unnoticed. People assess risk thinking only about the criminal aspect, and that's where they usually feel the least impact.
Criminal
It is the most remembered and slowest process. In many cases, it depends on the victim's representation and can end in a settlement, which gives the false impression that "nothing came of it".
Civil
This is what hurts the wallet. Violation of privacy generates a duty to compensate for moral damages, and here we are not discussing imprisonment, we are discussing value. The process continues independently of the criminal outcome.
The ongoing family process
It is the most decisive and least predictable factor. In custody or divorce disputes, the behavior of the person who monitored the situation weighs heavily in the court's assessment of co-parenting and the ability to respect boundaries. The person enters trying to prove something about the other and leaves having to explain themselves.
Who else is responsible besides the person who installed it?
Responsibility is not limited to the person who touched the device.
- Who asked for it?. Committing someone else to the installation does not exempt the person who commissioned it; on the contrary, it creates two parties responsible.
- Who forwarded the content?. Receiving a conversation obtained improperly and forwarding it to the family group creates personal liability, especially when the material is intimate.
- Who lent their account or card? for the contracting of the service, when it becomes clear that the purpose was known.
- The employer, This occurs when employee monitoring goes beyond the limits of what was communicated and agreed upon. The company is liable in labor court even if no one is criminally prosecuted.
There is also the reputational effect in regulated professions. Lawyers, doctors, civil servants, and police officers are also held accountable by their professional councils or internal affairs departments, with their own independent procedures.
What changes when a protective order is in place?
If a protective order is in effect, the situation changes significantly. Orders for separation and prohibitions on contact extend to electronic means. Monitoring the messages, location, or social media of the protected person can be interpreted as a violation of the order, which is a separate crime and punishable by imprisonment.
In this context, the argument of a shared device or a family plan is also invalid. If the line is still in the name of the person who was removed from the relationship, the solution is to transfer ownership, not use the contract as an entry point.
Signs that the situation has already crossed the line.
- To find out about trips that weren't reported to you.
- Commenting on conversation content that you did not participate in.
- Appearing in places by repeated coincidence.
- Demand an explanation for social media activity seen at an unlikely time.
If you were the person being monitored
The order of actions matters, because some measures erase precisely what could serve as evidence.
- Do not uninstall anything before registering. Take a screenshot of the app's screen, including its name and the date. Deleting it first and reporting it later leaves you with nothing.
- File a police report. In most states this is done online. Describe what you found and since when.
- Change the passwords on another device., Not the compromised cell phone. Start with the primary email, which is the key to recovering everything else.
- Close open sessions In messaging and cloud accounts. Every major service has a list of connected devices in its security settings.
- Enable two-step verification In everything, starting with email, messaging apps, and app store accounts.
- Review who has legitimate access.Family sharing, shared location, linked backup accounts, device pairing on the watch or in the car. A lot of "surveillance" works by permission granted and then forgotten.
- Seek legal advice. If a relationship is involved, free legal assistance is available at the Public Defender's Office and at legal aid clinics in law schools.
If there is a threat or history of violence, protective measures come before any technical intervention. The cell phone can be replaced later; physical security cannot wait.
