Firewalls & Restricting Outbound Traffic
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The only ports that really matter to block are 25, 80 and 443. You can't really block 80 and 443, but you can force them through a proxy. If you are leaving these open, blocking anything is just a waste.
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@scottalanmiller said in Firewalls & Restricting Outbound Traffic:
The only ports that really matter to block are 25, 80 and 443. You can't really block 80 and 443, but you can force them through a proxy. If you are leaving these open, blocking anything is just a waste.
DNS is good to block if you want to skip using a proxy and jsut restrict based on DNS. In that case you lock it down to only allow DNS out fromthe DNS servers. Or from everything, but only TO your specifically allowed external DNS (such as Strongarm.io's DNS)
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@JaredBusch said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
@scottalanmiller said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
@scottalanmiller said in Firewalls & Restricting Outbound Traffic:
Is there really any reason to be blocking all of the ports? I mean it's fine, but will the additional security offset the potential problems?
The only reason is to try to limit what can initiate connections to the outside from inside our network. I've been wondering this myself, and am not sure. I'm not sure what problems will arise. I know there will be a period of time where "this" doesn't work or "that" doesn't work because they were things I didn't consider and/or forgot about...but in theory it should normalize. Who knows, if I do decide to do this it may turn into a nightmare and I'll end up throwing in an "any any" statement.
Might not normalize. New software will need different ports over time, so it might be a continuous pain. Malware mostly uses the ports you've opened, almost exclusively. So the question is, I think, is ANY pain worth ZERO protection?
Well if it's "zero" then no. But I don't think it's zero. How close to zero, who knows.
Seriously, do not block shit. It causes nothing but problems and solves not a damned thing.
Not a single piece of effective malware on the planet uses anything except port 80 or port 443. Why? Because without those ports open no one can do anything. So they HAVE to be open. Why code your malware so that it can be trivially blocked by a home user?
Blocking port 25 is great, to prevent spam leaving your network, but aside from that, there is no benefit to restricting everything.
I can telly ou that you are already in for headaches by thinking you can not open the Teamviewer port when you know for a fact that the application is used.
This is exactly the idiotic mentality that drives bad decisions. Think don't feel. When you think, you will see that there is ZERO upside to this type of blocking.
This is pretty much my logic too.
What is it you are actually trying to block from going out? Incoming is what you want to focus on, not outgoing for a typical SMB. As Jared said, it will end up being a complete headache sooner than later.
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@scottalanmiller said in Firewalls & Restricting Outbound Traffic:
@dafyre said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
@scottalanmiller said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
@scottalanmiller said in Firewalls & Restricting Outbound Traffic:
Is there really any reason to be blocking all of the ports? I mean it's fine, but will the additional security offset the potential problems?
The only reason is to try to limit what can initiate connections to the outside from inside our network. I've been wondering this myself, and am not sure. I'm not sure what problems will arise. I know there will be a period of time where "this" doesn't work or "that" doesn't work because they were things I didn't consider and/or forgot about...but in theory it should normalize. Who knows, if I do decide to do this it may turn into a nightmare and I'll end up throwing in an "any any" statement.
Might not normalize. New software will need different ports over time, so it might be a continuous pain. Malware mostly uses the ports you've opened, almost exclusively. So the question is, I think, is ANY pain worth ZERO protection?
Well if it's "zero" then no. But I don't think it's zero. How close to zero, who knows.
The best advice I can offer is to block only outgoing ports that you KNOW are going to be issues... like Port 25... for anything but an email server... and Port 53 for anything but your internal DNS servers...
The way I would do it for outgoing
block 25 [except for internal emali server] block 53 [except for internal DNS servers] block 138,139,445 [SMB share traffic] block 1433 [SQL Server] block 3306 [MySQL / MariaDB]And allow most everything else.
I'm sure there are others... but that would be my starting point.
When would you want to block outgoing DNS, outgoing MySQL and so forth? While rarely used, if you need them, you need them. What's the value in blocking them?
My post was after some of the others that would have made me rethink this.
I'd block port 53 except for my internal DNS servers to devices and/or malware from bypassing corporate DNS.
Port 25 is a given. The others may be a little over kill.
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@JaredBusch said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
@scottalanmiller said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
@scottalanmiller said in Firewalls & Restricting Outbound Traffic:
Is there really any reason to be blocking all of the ports? I mean it's fine, but will the additional security offset the potential problems?
The only reason is to try to limit what can initiate connections to the outside from inside our network. I've been wondering this myself, and am not sure. I'm not sure what problems will arise. I know there will be a period of time where "this" doesn't work or "that" doesn't work because they were things I didn't consider and/or forgot about...but in theory it should normalize. Who knows, if I do decide to do this it may turn into a nightmare and I'll end up throwing in an "any any" statement.
Might not normalize. New software will need different ports over time, so it might be a continuous pain. Malware mostly uses the ports you've opened, almost exclusively. So the question is, I think, is ANY pain worth ZERO protection?
Well if it's "zero" then no. But I don't think it's zero. How close to zero, who knows.
Seriously, do not block shit. It causes nothing but problems and solves not a damned thing.
Not a single piece of effective malware on the planet uses anything except port 80 or port 443. Why? Because without those ports open no one can do anything. So they HAVE to be open. Why code your malware so that it can be trivially blocked by a home user?
Blocking port 25 is great, to prevent spam leaving your network, but aside from that, there is no benefit to restricting everything.
I can telly ou that you are already in for headaches by thinking you can not open the Teamviewer port when you know for a fact that the application is used.
This is exactly the idiotic mentality that drives bad decisions. Think don't feel. When you think, you will see that there is ZERO upside to this type of blocking.
Who said I wasn't thinking? It's the whole reason I started this post...to get discussion on something I'm brainstorming. Good information nonetheless.
BTW, I do not think that I cannot open the TeamViewer port...it was simipy a "can I get away with it using the alternate 80/443?" If not, then I'd open the port.
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Ok, so perhaps the discussion should be...which ports would you blanket block?
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@anthonyh said in Firewalls & Restricting Outbound Traffic:
Ok, so perhaps the discussion should be...which ports would you blanket block?
- That's it. And it is blocked on every network I have ever had access to the core router of.
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@JaredBusch said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
Ok, so perhaps the discussion should be...which ports would you blanket block?
- That's it. And it is blocked on every network I have ever had access to the core router of.
You wouldn't want to force DNS at least, too? I'm liking the idea that DNS requests must be made by my DCs. Maybe it's not necessary.
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@anthonyh said in Firewalls & Restricting Outbound Traffic:
@JaredBusch said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
Ok, so perhaps the discussion should be...which ports would you blanket block?
- That's it. And it is blocked on every network I have ever had access to the core router of.
You wouldn't want to force DNS at least, too? I'm liking the idea that DNS requests must be made by my DCs. Maybe it's not necessary.
That is not an IT blanket decision.
That is a company policy decision.
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@anthonyh said in Firewalls & Restricting Outbound Traffic:
Who said I wasn't thinking? It's the whole reason I started this post...to get discussion on something I'm brainstorming. Good information nonetheless.
I was not specifically saying you were not. I tend to generalize because while it is a response to your thread, this is a broader discussion.
BTW, I do not think that I cannot open the TeamViewer port...it was simipy a "can I get away with it using the alternate 80/443?" If not, then I'd open the port.
If you went this route, you simply open it. You do not block it and open it if there is a problem.
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@anthonyh said in Firewalls & Restricting Outbound Traffic:
Ok, so perhaps the discussion should be...which ports would you blanket block?
Just 25 under normal circumstances, and not because it send out our data but because it is a means of being a spam host, a slightly unique case and pretty much the only one that involved port blocking as an effective method of stopping something.
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@anthonyh said in Firewalls & Restricting Outbound Traffic:
@JaredBusch said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
Ok, so perhaps the discussion should be...which ports would you blanket block?
- That's it. And it is blocked on every network I have ever had access to the core router of.
You wouldn't want to force DNS at least, too? I'm liking the idea that DNS requests must be made by my DCs. Maybe it's not necessary.
Are there cases for that? Okay. But you already control that in other ways. So I'm unclear what benefit you think that this will provide since you are talking about malware, not your users. Does malware looking things up on your DC provide some value to you?
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@scottalanmiller said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
@JaredBusch said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
Ok, so perhaps the discussion should be...which ports would you blanket block?
- That's it. And it is blocked on every network I have ever had access to the core router of.
You wouldn't want to force DNS at least, too? I'm liking the idea that DNS requests must be made by my DCs. Maybe it's not necessary.
Are there cases for that? Okay. But you already control that in other ways. So I'm unclear what benefit you think that this will provide since you are talking about malware, not your users. Does malware looking things up on your DC provide some value to you?
We have a log collector that does DNS analysis. So, yes, it does actually. And if I decided to "black hole" a DNS record (have done this as past jobs, but not this one yet), there would be no way around it.
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Let's ask another question... we've all had port blocking for decades, this is not a new feature. Is anyone port blocking? If so, why? Has it ever had benefits?
I've worked for places that port blocked, but it was solely because they didn't want their users to be able to do anything. Which if that is your goal, okay. But it clearly is not, you want your users to be able to do things that they want to do, which I totally support. But I don't know what the purpose of the port blocking would be then since we've always been able to do it and never found it valuable before. Why start doing it now in an era where the value to doing so is gone when we didn't when there used to be some value to it.
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@anthonyh said in Firewalls & Restricting Outbound Traffic:
@scottalanmiller said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
@JaredBusch said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
Ok, so perhaps the discussion should be...which ports would you blanket block?
- That's it. And it is blocked on every network I have ever had access to the core router of.
You wouldn't want to force DNS at least, too? I'm liking the idea that DNS requests must be made by my DCs. Maybe it's not necessary.
Are there cases for that? Okay. But you already control that in other ways. So I'm unclear what benefit you think that this will provide since you are talking about malware, not your users. Does malware looking things up on your DC provide some value to you?
We have a log collector that does DNS analysis. So, yes, it does actually. And if I decided to "black hole" a DNS record (have done this as past jobs, but not this one yet), there would be no way around it.
You think that malware would have no way around it? It would just use port 80 or 443. There is always a way around it.
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@scottalanmiller said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
@scottalanmiller said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
@JaredBusch said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
Ok, so perhaps the discussion should be...which ports would you blanket block?
- That's it. And it is blocked on every network I have ever had access to the core router of.
You wouldn't want to force DNS at least, too? I'm liking the idea that DNS requests must be made by my DCs. Maybe it's not necessary.
Are there cases for that? Okay. But you already control that in other ways. So I'm unclear what benefit you think that this will provide since you are talking about malware, not your users. Does malware looking things up on your DC provide some value to you?
We have a log collector that does DNS analysis. So, yes, it does actually. And if I decided to "black hole" a DNS record (have done this as past jobs, but not this one yet), there would be no way around it.
You think that malware would have no way around it? It would just use port 80 or 443. There is always a way around it.
I suppose that's true. They could also go out another random port since none of it would be blocked.
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@anthonyh said in Firewalls & Restricting Outbound Traffic:
@scottalanmiller said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
@scottalanmiller said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
@JaredBusch said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
Ok, so perhaps the discussion should be...which ports would you blanket block?
- That's it. And it is blocked on every network I have ever had access to the core router of.
You wouldn't want to force DNS at least, too? I'm liking the idea that DNS requests must be made by my DCs. Maybe it's not necessary.
Are there cases for that? Okay. But you already control that in other ways. So I'm unclear what benefit you think that this will provide since you are talking about malware, not your users. Does malware looking things up on your DC provide some value to you?
We have a log collector that does DNS analysis. So, yes, it does actually. And if I decided to "black hole" a DNS record (have done this as past jobs, but not this one yet), there would be no way around it.
You think that malware would have no way around it? It would just use port 80 or 443. There is always a way around it.
I suppose that's true. They could also go out another random port since none of it would be blocked.
If you block ALL ports, then you can make cases for all kinds of stuff. But leave any open, and you might as well leave them all open, except for 25.
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@scottalanmiller said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
@JaredBusch said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
Ok, so perhaps the discussion should be...which ports would you blanket block?
- That's it. And it is blocked on every network I have ever had access to the core router of.
You wouldn't want to force DNS at least, too? I'm liking the idea that DNS requests must be made by my DCs. Maybe it's not necessary.
Are there cases for that? Okay. But you already control that in other ways. So I'm unclear what benefit you think that this will provide since you are talking about malware, not your users. Does malware looking things up on your DC provide some value to you?
You cannot force client DNS 100% of the time to be what you want in a BYOD environment. If DNS control is a desire, blocking DNS at the router is the simpler method.
It is unrelated to the blanket blocking discussion as it is a decision the business needs to decide if they need to make or not.
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@JaredBusch said in Firewalls & Restricting Outbound Traffic:
@scottalanmiller said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
@JaredBusch said in Firewalls & Restricting Outbound Traffic:
@anthonyh said in Firewalls & Restricting Outbound Traffic:
Ok, so perhaps the discussion should be...which ports would you blanket block?
- That's it. And it is blocked on every network I have ever had access to the core router of.
You wouldn't want to force DNS at least, too? I'm liking the idea that DNS requests must be made by my DCs. Maybe it's not necessary.
Are there cases for that? Okay. But you already control that in other ways. So I'm unclear what benefit you think that this will provide since you are talking about malware, not your users. Does malware looking things up on your DC provide some value to you?
You cannot force client DNS 100% of the time to be what you want in a BYOD environment. If DNS control is a desire, blocking DNS at the router is the simpler method.
It is unrelated to the blanket blocking discussion as it is a decision the business needs to decide if they need to make or not.
What's the difference between blocking DNS at the router vs firewall? The idea being only permitted DNS servers would be allowed to perform DNS requests to the outside world. Everything on the inside would need to use the on premis DNS servers (aka our DCs).
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@anthonyh said in Firewalls & Restricting Outbound Traffic:
What's the difference between blocking DNS at the router vs firewall?
Those are the same thing. All routers on the market for the last two decades is a firewall. And all firewalls that I know of are routers. Since the late 1990s, while a router and firewall are different functions and aspects, all real world products are always both. So those terms are actually interchangeable unless you are discussing the functionality.
