Hey guys so basically this is for my friend Layla lol she is 28, works remotely, lives alone in an apartment and she has been getting this really weird feeling that someone might be tracking her phone without her knowing. Like her battery drains super fast, her phone gets hot for no reason, and sometimes she sees the camera light flicker when she is NOT using any app. She does not want to go to the police yet because she has no proof. So the question is, how can you actually tell if someone is on your phone without permission? She wants technical steps, apps she can use, and a proper guide. Anyone been through this? What do you do?
Ok so let me break this down properly because Layla situation is actually more common than people think and there are real technical signs to look for 
First thing, battery drain. If a hidden tracking app is running in the background it will constantly use CPU cycles to send location pings or screen data. Go to Settings > Battery > Battery Usage and check which apps are eating the most power. If you see something you never installed or something with a weird generic name at the top of that list, thats a red flag.
Second, data usage spike. Go to Settings > Mobile Data or Network Usage and look at which apps have been sending data even when you are not using them. A tracker will upload info to a remote server, so it needs internet access. If some random app you dont recognize used 200MB in the background, that is suspicious.
Third, the camera flicker she mentioned. On Android go to Settings > Privacy > Permission Manager > Camera and check every app that has access. Remove anything that should not have it. On iPhone go to Settings > Privacy and Security > Camera. Same thing.
Fourth, check for unknown device admin apps. On Android: Settings > Security > Device Admin Apps. If anything is listed there that you did not set up yourself, remove it immediately because admin level access means deep control over the device.
Fifth, run Malwarebytes Mobile or Certo Mobile Security (for iPhone). Both are solid and will scan for anything that should not be there 
The combo of fast battery drain + data spikes + camera access = definitely worth a full scan ASAP.
Bro ModTechLab literally covered the basics perfectly… I just want to add one thing that a lot of people miss, check your phone temperature patterns.
If Layla phone is warm even when it is sitting on a table doing nothing, that means something is working in the background. Normal phones only get warm when you are gaming or doing heavy stuff. Background tracking apps run constant processes and that generates heat.
Also, go into Developer Options (on Android tap Build Number 7 times in About Phone to unlock it) and then go to Running Services. This shows you EVERY process currently active on the phone including hidden ones. Look for anything with a name you dont recognize. You can Google the process name if unsure.
One more thing, if she ever clicked a link from an unknown number or email, there is a chance a profile was installed. On iPhone go to Settings > General > VPN and Device Management. If you see ANY profile there that you did not install yourself that is a serious problem and you need to remove it right away and change all passwords immediately after 
Do not ignore that camera flicker thing either. That is probably the biggest red flag in the whole post tbh.
Okay adding onto what TechLiftPro said about profiles on iPhone, this is actually how a LOT of monitoring tools get onto phones without the owner knowing. Someone installs a configuration profile through a link that looks like a normal website or app. Once that profile is on your device it can reroute your traffic, read messages, and access mic or camera with no notification 
For Layla specifically since she works remotely, does she use a work phone or her personal phone for work stuff? Sometimes employers install MDM (Mobile Device Management) profiles on work phones and some of those have VERY deep access including screen monitoring and location tracking. If it is a work device that could actually be the answer to her question and it might be legal depending on her contract.
But if it is her personal phone and she never agreed to any profile then that is a different story entirely. Either way the steps from ModTechLab and TechLiftPro are the right move. Start with the profile check and battery usage. Those two things alone will tell you a lot. And yea run Malwarebytes. Free version works fine for a basic scan 
Wait Byteforge44 just reminded me of something, Layla said she lives alone right? So who had physical access to her phone? Because most of these tracking tools require someone to physically have your phone for at least 5 to 10 minutes to install them. They cant just magically appear unless she clicked a bad link.
Think about who has been around her lately. An ex, a roommate from before, a family member who she lent the phone to? That narrows things down a lot.
Also I want to flag something nobody mentioned, check your Google account or Apple ID for logged in devices. On Google go to myaccount.google.com > Security > Your Devices. On Apple go to Settings > tap your name at top > scroll down to see all devices. If you see a device name or location you do not recognize REMOVE IT immediately and change your password and enable two-factor authentication.
This is a step people always skip and it is honestly one of the most important ones. If someone has access to your Google or Apple account they can track your location through Find My Device or iCloud without ever touching your phone again 
Okay real talk, I went through something similar with my old phone and let me tell you it was a whole nightmare.. My phone was getting hot every single night after like 11pm. Always around the same time. At first I thought it was just charging but then I noticed it was happening even when the phone was NOT plugged in.
I ran Malwarebytes and it found nothing. Ran another app called Incognito, App Scanner and THAT one flagged a system level app that had mic permissions it should not have had. It was buried under a generic name like “System UI Service” or something like that. Completely invisible on the home screen.
What I ended up doing was a full factory reset which sounds scary but it completely wiped everything. Before doing that I backed up only my photos and contacts, NOT apps or system backups because those can carry the problem over.
After the reset the heat issue stopped completely overnight. So sometimes the nuclear option is the cleanest solution. If Layla is not finding anything with the scan apps and still has a bad feeling, reset might be the way to go. You lose some stuff but you get your peace of mind back and that matters more 
Alright since people keep asking for a proper step by step guide, here it is. This is what I personally walk people through when they come to me with this issue 
STEP 1, CHECK BATTERY USAGE
Go to Settings > Battery > Battery Usage (last 7 days). Look at the full list not just top apps. Anything using more than 10 to 15 percent that you dont recognize = investigate.
STEP 2, CHECK DATA USAGE
Settings > Network > Data Usage (or Mobile Data on iPhone). Sort by highest usage. Check background data specifically. A tracking tool running in background will always need data to send info out.
STEP 3, REVIEW APP PERMISSIONS
Settings > Privacy > Permission Manager. Check Camera, Microphone, Location separately. Remove permission from anything that does not need it. Be strict about this.
STEP 4, CHECK DEVICE ADMIN (Android only)
Settings > Security > Device Administrators. Nothing should be there unless you set up a work email or remote wipe yourself. Remove anything unfamiliar.
STEP 5, SCAN WITH TRUSTED APPS
Download Malwarebytes (free), Certo (for iPhone), or Incognito App Scanner. Run a full scan. Do not install random security apps from unknown developers because some of those are actually the bad thing you are looking for.
STEP 6, REVIEW LINKED ACCOUNTS
Check myaccount.google.com or Apple ID settings for unknown devices and active sessions.
STEP 7, FACTORY RESET IF NEEDED
Last resort but most effective. Backup photos and contacts only, not full system backup. Then reset. 
Follow these in order. Do not skip steps.
cyphernova that guide is actually really clean, Bookmarking this whole thread tbh.
I want to add one thing for the iPhone users specifically since Layla might be on iOS, there is this thing called Lockdown Mode that Apple added. It is in Settings > Privacy and Security > Lockdown Mode. Turning it on blocks a LOT of attack methods including certain types of profiles and network tracking. It does limit some functionality but if someone genuinely thinks they are being watched it is worth it temporarily.
Also for both Android and iPhone, check if your WiFi network itself is compromised. If the router in her apartment was accessed by someone else, they can monitor ALL traffic going through it including what apps are sending data, what sites she visits, etc. You can use an app called Fing (free) to scan your network and see all connected devices. If you see something on your home network you dont recognize, change the router password immediately and reboot it.
Network level monitoring is something a lot of people forget to check because they focus only on the phone itself. But the router is actually an easier place to set up monitoring than the phone in many cases 
Okay so speaking of apps, I have personally used a few and I want to give real opinions not just a random list 
MALWAREBYTES MOBILE, Free, available Android and iOS. This was the first one I tried when I had a sketchy situation with my phone after my ex had access to it for a weekend. It is straightforward, does not require any technical knowledge, and the scan takes like 3 minutes. Found nothing on my phone that time but I know people who it has flagged things for. 9/10 would recommend as a starting point.
CERTO MOBILE SECURITY (iPhone), This one is specifically built for iOS and is honestly more thorough than Malwarebytes on Apple devices. It checks for suspicious profiles, checks backup files, and flags apps that have more permissions than they should. Slightly more technical but the free version still gives you a solid report. 8/10.
INCOGNITO, APP SCANNER (Android), This one found the issue on my phone eventually (mentioned it in my earlier comment lol). It is specifically designed to find apps that are hiding or using permissions sneakily. The UI is simple and it explains what it found in plain language. 9/10.
GLASSWIRE, More of a network monitor than a scanner. It shows you in real time what each app is sending data to and when. Super useful for catching something that checks in with a remote server at night. 8/10.
FING, For checking your WiFi network as TitanMatrix mentioned. Free and really easy to use. 9/10.
Do not download random “anti-tracking” apps from sketchy developers. Stick to these known ones 
NeuroFluxis thank you for the real reviews because I was literally about to ask which apps are actually worth it. People always just say “download a security app” without telling you which ones dont just steal your data themselves lol
For Layla I want to add something from a slightly different angle. The camera flickering she mentioned, on newer Android phones there is actually a green dot indicator at the top right of the screen whenever the camera or mic is active. Same with iPhone, it shows an orange dot for mic and green for camera. If she is seeing those dots when she is not in any app, that is pretty solid evidence something is running in the background accessing those sensors.
Go to Settings > Privacy > Privacy Dashboard (Android 12 and up) and it shows you a full timeline of which apps accessed camera, mic, and location in the last 24 hours. If you see an access at 3am when you were asleep, that tells you everything you need to know 
Apple has a similar feature in Settings > Privacy > App Privacy Report. Enable it and let it collect data for a day or two then review the report. It is honestly kind of shocking how many apps are doing stuff in the background even on a normal phone.
Okay I am going to be the slightly sarcastic one here lol, the fact that we live in a world where you need a 10-step guide to check if your own phone is being used against you is wild to me Like we are literally carrying tiny surveillance computers in our pockets and acting surprised when someone figures out how to use that against us.
BUT in all seriousness, everything in this thread is gold and I want to highlight something SynapseVector121 said earlier that people keep scrolling past. The ACCOUNT access thing is huge. You do not need to have a tool installed on the phone to track someone. If you have their Google or Apple account credentials you can see their location in real time through built in features that are totally normal and legitimate. Find My, Google Maps sharing, Family Sharing, all of these can be used without the target knowing if they have never checked those settings.
So Layla should absolutely check: Settings > Privacy > Location Services > Share My Location (iPhone) and also check if she accidentally has Google location sharing turned on with someone through Google Maps. Open Google Maps > tap your profile > Location Sharing. If anyone is listed there and she did not put them there, remove them right now
Simple thing, massive impact.
Cynerion making the most important point of the whole thread with zero fanfare 
The location sharing through Google Maps and Apple is SO often overlooked and it requires zero technical skill to set up which is what makes it dangerous.
I work in IT support and you would be amazed how many people come to me thinking their phone has some advanced tool on it and it turns out they just have location sharing enabled with someone from like 2 years ago. Like they set it up when they were in a relationship or when they wanted to share location with a parent and then completely forgot about it.
For anyone reading this thread, right now, today, go check your location sharing settings. On iPhone it is Settings > Your Name > Find My > Share My Location and also check inside the Find My app under the People tab. On Android open Google Maps, tap your profile picture, tap Location Sharing. See who is on that list. If anyone is there that you did not intentionally add in the last few weeks, remove them and review how that got set up.
Takes 2 minutes. Could change a lot. 
And yeah Layla please do this first before going through all the technical scans, it might literally be the answer.
Okay can we talk about the phone heat thing for a second because I feel like that detail from the original post is being underrated.
Phones generate heat from the processor. The processor works hard when it is running tasks. If the phone is hot while sitting on a table not plugged in with the screen off, the processor is doing something. There are only a few reasons that happens naturally, a bugged app that is crashing in a loop, downloading a large update, or something running deliberately in the background.
Layla said it happens randomly. That makes the update scenario unlikely. The most likely answer is either a buggy app or something running on purpose. To check: when the phone is hot, immediately go to Settings > Battery > Battery Usage and look at what is on top RIGHT AT THAT MOMENT. The problem app will be right there eating the most battery.
You can also use an app called CPU-Z (Android) or iStatistica (iPhone) to get real time processor and temperature data. CPU-Z is free and shows you exactly which cores are running hot and which processes are using them. It is a bit more nerdy but if you want the actual numbers it gives you that.
The heat is actually one of the most reliable indicators because it is hard to fake and hard to hide 
Reading this whole thread like 
because I have a friend in almost the exact same situation as Layla and I am sending this thread to her right now.
The one thing I want to add, and this is something nobody has said yet, is about weird behavior in calls. If during phone calls Layla hears slight echo, clicking sounds, or a very faint background noise that was not there before, those can sometimes be signs that the call audio is being captured or routed somewhere else. Now I am not saying every bit of static means something, but if it is consistent and combined with all the other signs Layla is seeing, it is worth noting.
Also, check SMS for any messages that look like random gibberish that you never sent. Some older tracking tools used to send coded SMS messages in the background to report data. On newer phones this is less common because they use internet instead, but older or cheaper phones might still trigger this. Go to your sent messages folder and look for anything you do not remember sending.
And one final thing, if you are going to do a factory reset like zerophantom mentioned, make sure you do NOT restore from an iCloud or Google backup unless you know exactly when the problem started. Restore only from a backup that predates when the issues began. Otherwise you might just put the same problem right back on your fresh phone 
Okay so after reading literally every reply in this thread here is my final summary for Layla or anyone else in this situation 
The community here basically covered everything in perfect order. Start with the simple stuff: check location sharing on Google Maps and Find My, check which devices are logged into your Apple ID or Google account, and review app permissions for camera and mic. These three things take under 10 minutes and will catch the most common situations.
If those come up clean, move to the scan level: run Malwarebytes or Incognito App Scanner, check your Privacy Dashboard or App Privacy Report for weird access times, and use GlassWire to monitor what your apps are sending out overnight.
If STILL nothing shows up but the signs are still there, the heat, the battery, the camera light, then look at your router with Fing and consider a clean factory reset.
What I love about this thread is that nobody got dramatic or paranoid. The advice here is practical, it respects Layla privacy and safety, and it gives her real tools to understand what is happening with her own device. That is how this stuff should be handled.
Stay safe out there everyone. And props to ThreadMiner for actually asking the right questions instead of just panicking 
This thread is going in my saved folder for real.