Why router settings get changed making it no access to internet

Hi,
Of late, it has become to my notice that there are programs which will penetrate the router and change the dns server settings making it an annoying experience not to have any internet access, though all the lights are glowing in the modem.
There is no other go other than resetting the router and getting it reconfigured by the configurer of the ISP. The user has to resort to this step, as again, the malware or something is changing again the router settings making you to again reset. I have done enough resetting and had frequent problems even in accessing my normal router page.
The main draaaw back of this is non updated firmware by the suppliers of the modem for their products. So, some vulnerabilities are found in the rom 0 section of the router software page.
Is there any sollution to the above, other than resetting and re configuring.
Some times, you have to get the internet access by supplying the access points, in the router, which is not easy if you cannot access the router page.
If suppose, we use the av to resolve this, then there is a problem, it is changing something, which you may not know again resulting in no internet access, or not a valid local area connection ips message.
The computer just shows as problem in modem always and ask you to reset or power off ang try. The microsoft could not troubleshoot this problem till now for windows 7

If this were happening to me and I couldn't find/fix the problem I would buy a new router! But only after isolating the router from computers on the LAN to see if it was a specific computer on my lan that was affecting it.

If you want more help you are going to need to specifiy here what modem (cable? DSL? Satellite?) you are talking about, and the specific model and revision of the router.

Hi, my modem is tdsl w2 type 2 adsl2+cpe/wireless router.
Why auto detect does not work for me, saying that it is unidentified network. I have to again insert some values to the use the following values in ip field including gateway. I prefered dns server of google which is 8888 and 8844 with dots/ This is teracom company supplied router procured and sold by my service provider.
It is more than one year , so no replacement is possible.
Please could you expand on why this behaviour