trust me, we’re all like that at that age, and always have been.
relevant: https://www.youtube.com/watch?v=ltbluBU0pQY&t=2m38s
Sorry for the walls of text.
If you have a significant other that also involved with your son’s life, talk to him/her about what should be talking to your son about. If you’re a single mom, reach out to other parents or guidance counselor (secular or spiritual) for advice.
Asking for opinions on a forum is helpful, but ultimately nothing more than the biased opinions of others who don’t know the full circumstances of your situation.
My last (probably) words of (biased) advice is the main thing is to open and strive to keep open a dialog with your son. With your son at 15, you’re in for decades of shocks and surprises, hopefully more good than bad!
Best of wishes and prayers to you.
lingyi
When I was 15 looking at porn (or at least dirty pictures) took a lot more effort than it does today.
One by one now:
If he didn’t use swear words with friends he’d probably be considered as kind of odd. He doesn’t use them when talking to you, which means he respect you. Mark that down as a plus.
Looking at porn. Have you guys had an open and complete talk about sex with him? If not, have it now. Sometimes kids look at porn out of curiosity, and to learn what our culture considers a big deal. Back in the good old days there was not one father’s stash of Playboys which did not get raided by his teenage sons.
Make sure he knows why real life is different from porn. I’d be worried if he was looking at the weirder stuff out there. And better porn than sex.
As for inappropriate conversations, make sure he knows the legal issues which others have mentioned. Make sure he knows about spoofing which others have also mentioned. And especially make sure he knows that anything he writes on line can be copied and spread all over. And I’m not sure what kind of inappropriate conversations you are talking about. It can range from double entendres all the way up to nude pictures. Mostly, talking is better than sex.
There are plenty of 15 year olds having sex, way too young in my fuddy duddy opinion. But does he know how to protect himself and the girl if he does it anyway?
We have two daughters, both now married, and they were both on birth control long before it was necessary. And they never got into trouble. And it will make it easier for him to talk to you if he is having problems. Openness is tough on him and on you, but it pays dividends.
Remember, his being trustworthy is different from him staying 12 forever.
Teenage boys have not mutated into a different species. 
Trusting a teenager to not swear around his friends is a misplaced and useless trust. There is no valid reason for a teenager to talk to all his friends the same way he talks to his mother. Being shocked that boys swear is a small failure of parenting. But it’s not a harmful failure, just a minor learning experience for a mother to realize that “ordinary” swearing (as opposed to intentional personal insults), among teenage friends, IS definitely appropriate - regardless of what parents think or teach.
Thread title edited for clarity
So he swears around his friends and wants to see naked women - that is normal. I’ll tell you what’s not normal. My 18 year old nephew who has been so sheltered and controlled his whole life that he’s never had a girlfriend, doesn’t ever swear, smoke or drink. He is completely lost in the adult world he is entering. He has minimal social skills because he never got a chance to be his own person and learn about limits. I’m guessing that once he is free of his parents he’s either going to get some girl pregnant or end up drinking and driving.
Kids have to spread their wings and if you keep him under your thumb he’s going to resent you for it.
Read it again without being so defensive. It’s good insight. You’ve already violated your son’s privacy by snooping into his online chat account. That’s the equivalent of spying on his private conversation among friends. You shouldn’t be surprised that he talks differently around friends than he does with his parents. As Little Nemo mentioned, it’s a good time to have a talk with him about boundaries, but it’s going to be difficult to do that considering the boundaries you’ve crossed. I can only imagine how the conversation might go: “Give me your password so that I can read all of your intimate, personal secrets and private conversations you’ve had with your friends and girls. Then we’re going to talk to you about boundaries, mister!” Good luck with that.
He’s a normal 15 year old boy. How’s his grades? How’s his behavior in public? Around your friends and family? Around teachers?
There’s no reason for you to stop trusting him.
At the end of the day, it might come down to fairness. Children have a natural sense of fairness, until it is eroded by authorities acting in ways they see as unfair.
He will trust you only as long as he perceives you as being fair. That means fair rules, fair enforcement of the rules, fair process for dispute resolution, fair retribution for wrongs.
If he does not see you as fair, things will get worse. You have power. Don’t give him reason to believe you are abusing power.
Snooping on his phone IS reason to believe she’s abusing power. An easy test: would it be acceptable for the son to do the same with the mother’s phone? Oh horrors no? Well then…
There ARE good occasions for a mother to snoop on a son’s phone, and they are the exact same occasions when it’s good for a teenage son to snoop on his mother’s phone: reasonable and substantiated suspicion of criminal activity, hmmm what else - well, anything where if you were doing it you would hope he’d snoop on you.
If I were a parent, I’d search his computer, his room, his phone, everything! If he asked me “Do you have a warrant to do that?”, I’d pull out his birth certificate and say “Yes, here! And it’s valid until you move out!” :mad:
BTW, I say this with all conviction because I know what I would have done if I didn’t have my heart to heart conversations with my parents. They treated me like an adult at a young age and I tried my best to live up to that covenant.
I do disagree with no phone disclosure. My older kids never had cell phones as young teens. But my baby had a screen in front of her face from a very young age. I insisted on full disclosure of passwords. And I looked regularly. I caught a couple of hairy situations that could’ve went south fast if an adult didn’t act.
The older she got, the less I insisted. I trusted her behaviour and decision making skills by the time she was 16 and driving. I would’ve never let her in a car alone if I didn’t. It’s all a matter of giving and getting respect and trust.
If it helps any, Telli, you actually lucked out with him getting to fifteen before you got your nose metaphorically rubbed into his hormone induced indiscretions. Pity my poor son, who’s been going through all of this, plus sexting and a few other alarming things, with his twelve year old stepdaughter. Let’s just say that co-parenting is hard and leave it there, and nobody is ever ready for these disclosures. Just try not to think of all the crazy ass shit you and your friends were up to at that age–that way lies madness. 
To those who speak of a child’s Right to Privacy, where does that fit into your obligation as a parent to strive to prevent your child from engaging in potentially illegal activity? At least in the U.S., it’s illegal for anyone under 18 to view pornography, which Merriam-Webster defines as “the depiction of acts in a sensational manner so as to arouse a quick intense emotional reaction”. Note I’m not talking about nudity which does not fit the definition of pornography. Also illegal is underage sexting, which may be prosecuted as child pornography. What if the child is actually viewing or creating child pornography, which they may easily do by exposing themselves on their webcam.
What if the child is engaged in discussions of racially motivated, anti-government or any number of subversive acts? As I stated before, what if the child is actively participating in the bullying of someone else that may lead to harm of the other person or the child themselves if the other person does a reverse search and finds the child’s address.
What happens when law enforcement shows up to arrest you and or your child for illegal downloads or movies? I’ve never heard a parent say “I knew what my child was doing was wrong, but I turned a blind eye.” What happens when your child says “Oh, you knew it was illegal, but you never said anything about it, so I figured it must be okay to do it plus more!”
What happens when they go to work and part of their work agreement is that the employer reserves to right to monitor their email and web activity? "But, my parents respected my “Right to privacy!”
I don’t see anywhere in the Child’s Right’s guidelines any “Right to privacy” or the right to act reciprocally to anything their parents do. Neither do I see a right to internet access or a cell phone*. There is a minor’s “Right to Privacy”, but that’s when they’ve been arrested and/or convicted of a crime and their “Right to privacy” is to not have their identity disclosed.
*Internet access or a cell phone may be required for a proper education, but does not mean they have a right to non-educational access.
"Children have two types of human rights under international human rights law. They have the same fundamental general human rights as adults, although some human rights, such as the right to marry, are dormant until they are of age, Secondly, they have special human rights that are necessary to protect them during their minority.[18] General rights operative in childhood include the right to security of the person, to freedom from inhuman, cruel, or degrading treatment, and the right to special protection during childhood.[19] Particular human rights of children include, among other rights, the right to life, the right to a name, the right to express his views in matters concerning the child, the right to freedom of thought, conscience and religion, the right to health care, the right to protection from economic and sexual exploitation, and the right to education.[2]
United Nations educational guides for children classify the rights outlined in the Convention on the Rights of the Child as the “3 Ps”: Provision, Protection, and Participation.[20] They may be elaborated as follows:
Provision: Children have the right to an adequate standard of living, health care, education and services, and to play and recreation. These include a balanced diet, a warm bed to sleep in, and access to schooling.
Protection: Children have the right to protection from abuse, neglect, exploitation and discrimination. This includes the right to safe places for children to play; constructive child rearing behavior, and acknowledgment of the evolving capacities of children.
Participation: Children have the right to participate in communities and have programs and services for themselves. This includes children’s involvement in libraries and community programs, youth voice activities, and involving children as decision-makers.[21]
In a similar fashion, the Child Rights International Network (CRIN) categorizes rights into two groups:[22][23]
Economic, social and cultural rights, related to the conditions necessary to meet basic human needs such as food, shelter, education, health care, and gainful employment. Included are rights to education, adequate housing, food, water, the highest attainable standard of health, the right to work and rights at work, as well as the cultural rights of minorities and indigenous peoples.
Environmental, cultural and developmental rights, which are sometimes called “third generation rights,” and including the right to live in safe and healthy environments and that groups of people have the right to cultural, political, and economic development.
Amnesty International openly advocates four particular children’s rights, including the end to juvenile incarceration without parole, an end to the recruitment of military use of children, ending the death penalty for people under 21, and raising awareness of human rights in the classroom.[1] Human Rights Watch, an international advocacy organization, includes child labor, juvenile justice, orphans and abandoned children, refugees, street children and corporal punishment.
Scholarly study generally focuses children’s rights by identifying individual rights. The following rights “allow children to grow up healthy and free”:[according to whom?][24]
Freedom of speech
Freedom of thought
Freedom from fear
Freedom of choice and the right to make decisions
Ownership over one’s body"
Here’s a real life example of “boys will be boys” and feigning ignorance gone wrong.
One my middle school’s music teacher (not mine) would “coincidentally” leave a copy of Playboy or Penthouse in the teacher’s drawer. At first some of the boys would just look at it, but soon discovered that if they left money in the drawer, additional copies would magically appear. It’s not as of the other music teacher or other teachers weren’t aware of it since there was only one music class. Again, I never participated in the exchange process.
Years later, I read a newspaper article that the teacher was found showing porn movies to some students in the room’s closet. It didn’t mention that anything else occurred, but the likelihood seems high.
When I was young, I brought up the title of a child rearing book he had on his headboard during an argument and he told me that was his prerogative as an adult to read what he wants. Then as now, I didn’t see any “right” to read what he was just because he monitored what I was reading.
It’s perfectly natural for a parent to keep an eye on their children’s activities to make sure such things aren’t happening. And that may include some eavesdropping. And when a parent doesn’t find those things they should be happy about it, and certainly never mention to the child that they were doing that.
There is a line. The line is difficult to define, and probably it’s different in each case, but for sure there’s a line that matters. Staying on the side of the line that allows your kids to trust you, and that shows them that you trust them, is important.
A kid who is sure that you don’t trust him has a very reliable and predictable response: “Fuck this, and fuck them too.” That is not a place you want to get to.
Discovery of the situations I’ve described require more than eavesdropping which may be intentional or not. They require active “Invasion of Privacy” to discover, whether by direct viewing / listening while the activity is occurring, through active monitoring software or after the fact (which is what the OP described).
Some families have the only computer in the common living area where anyone passing by can see/hear what’s going on. Again, non-educational computer, internet or phone use is NOT A RIGHT, it’s a privilege.
Maybe I’m just from another era, but phone conversations (on a landline) were done on the ONLY phone in a common area. When I got soap in the mouth because my Mom heard me use the F word on the phone (while talking to my friend), there was never then or now any thought of Mom eavesdropping. Using profanity in the house just wasn’t done! Now, I’m no angel, I used profanity with my friends (which my parents asked if I did and I confirmed) and strived to reduce it as I was told it demeans others. In my eyes, no less calling someone a racist name.
When my parents discovered my brother started smoking in his mid-teens, they agree that it was better he do it openly rather than hide. My Mom (who was the smoker) would buy and share her cigarettes with him. Again, not only illegal (though much more common in the 60’s and 70’s), but imagine if he got cancer (while they were still alive) from smoking. It may well have turned from “But, you said it was okay” to “F*** You, your inaction caused this to happen!”
Okay, I’m done. I’ll leave the last word to others.
To the OP, I haven’t seen you return, but best wishes and prayers for you and your family in this situation.
Parents DO need to be aware of what their kids are saying and doing, to an appropriate extent and appropriate level of detail. Of course. Nobody gets it perfect. But judging kids’ privacy issues with parents, luckily, is similar to playing horseshoes - close does count. 
Getting that tricky balance somewhere close to right, and making a brave effort to try to maintain it close to right, is good enough.
Trusting kids far too much and far too soon is a disaster. That’s clear.
**But trusting kids far too little/too late is just as bad of a disaster. **
Holding that middle ground somehow, is part of parenting.