Possible to access to the internal LAN if I know router pass

[marklodge]

Is it possible to gain access to the internal LAN via WAN login on a broadband (ADSL) router, if I know the router password?
I've heard that users should always change their default router passwords as this can be exploited to allow hackers to gain access to the internal LAN (computers connected to the router) and can gain access to files stored on every pc on that lan. Is this true? If yes, then how is it done? I have done some searching but came up with nothing. Please enlighten us on this matter.
I have also read some threads which says that certain ports should be forwarded to be able to gain access to the internal Lan, but this was not very clear.
What is a malicious user able to accomplish if he knows the password of my broadband (ADSL) router? (Besides knowing my WAN username & password and resetting my router)
Any comments will be much appreciated

[yourmysin]

There is a feature on many router/switch's called remote administration. This feature allows you to connect directly to your router through the WAN interface. This is usually disabled by default and password protected. If an attacker gets ahold of your remote administration session you are well in trouble.

Think about what a router does, it routes traffic from one network to another. It is very easy for a hacker to take control of a remote administration session to change your routing table to route all data from your network to his. From this, should he choose to capture and replay the data you are subject to a MITM attack.

The hacker could also change your dns server to a server which he controls. Then you could easily be subject to a phishing attack you are not aware of.

[marklodge]

Thanks for the reply
I do know it is dangerous if a hacker has your password as there a many ways your security could be compromised
But, from a security point of view I do want to know specifically if it is possible for a malicious user to actually directly access all computers on the internal LAN via the router WAN login.

[Rijnzael]

It depends on the router firmware. If it doesn't have any functionality to allow a remote attacker to access your LAN, they they can't. If it does have such functionality (VPN, port forwarding, routing table modification), then they can. This is all assuming they have access to the administration interface or some other sort of login, of course.

[marklodge]

It depends on the router firmware. If it doesn't have any functionality to allow a remote attacker to access your LAN, they they can't. If it does have such functionality (VPN, port forwarding, routing table modification), then they can. This is all assuming they have access to the administration interface or some other sort of login, of course.

Thank you for the reply.
so how is it done via port forwarding?
i mean, if you change the route table it will modify outgoing data, right?

[int3grate]

It depends on the router firmware. If it doesn't have any functionality to allow a remote attacker to access your LAN, they they can't. If it does have such functionality (VPN, port forwarding, routing table modification), then they can. This is all assuming they have access to the administration interface or some other sort of login, of course.

Thank you for the reply.
so how is it done via port forwarding?
i mean, if you change the route table it will modify outgoing data, right?

You usually have to be on the LAN to access the router and change the port forward settings, unless remote access is turned on (which it isn't by default on most routers). If it's a wireless router you could just jump on the LAN, access the router, and configure it however you like.