Error: can't update avast and some unknown attack found.

[Invocation]

Hi all, this is my first post and as such I'd like to say a sunny hello to all forum members. I'm from sunny Scarborough (it's just too hot for me today though) in good old Blighty....anyway enough of that.

The reason I posted was because: 1. I can't seem to update my copy of Internet Explorer 5 or 5.5 (not sure which one it is off hand) to at least version 6 and therefore I can't d/l a lot of the applications I'd like to. Whenever I try to install the IE 6 setup (I can d/l IE 6 btw it just wont install) I get this message:

Setup was unable to connect to the Microsoft download site or your system administrator's download server to retrieve the instruction file for the Setup program. This could be caused by proxy server settings on your computer that are not valid, a busy Internet, or other problems with your current Web browser.
Using your current browser, you should confirm that you can connect to the Internet by trying to connect to http://www.microsoft.com/ or your system administrator's download server.

After following the message above I can connect to the URL they suggest but I've no idea what the system administrator's download server is anyway or my proxy server settings plus I've tried many times and surely the net can't be busy everytime I try. Any ideas anyone please I'm thinking this may also be the reason I can't update avast? When I try to update I get:

Info about current update, last encountered error: Cannot connect to download 58.avast.com [Unknown 80]

The other thing is that mainly today but also yesterday I started getting this pop-up from avast at the bottom of my screen in red, blue and yellow:

DCOM Exploit keeps being blocked. Attack from 81.178.227.238.174 or 175 (it changes) tcp

Does anyone know what this is all about. Is it something dangerous or something that I should be worried about?

Thanks a lot (in anticipation) and my apologies for hitting you all with so many questions wrapped up in one deceiving thread title  

[Lisandro]

Setup was unable to connect to the Microsoft download site or your system administrator's download server to retrieve the instruction file for the Setup program.

When I try to update I get: Info about current update, last encountered error: Cannot connect to download 58.avast.com [Unknown 80]

Do you use a firewall? Which one?

The other thing is that mainly today but also yesterday I started getting this pop-up from avast at the bottom of my screen in red, blue and yellow:

DCOM Exploit keeps being blocked. Attack from 81.178.227.238.174 or 175 (it changes) tcp

It's strange but seems you don't have a firewall.

Messages like: Network Shield: blocked "DCOM Exploit" - attack from 81.178.115.162:135/tcp
are due to the RPC/DCOM exploit, which is a vulnerability that allows an attacker to gain access to the destination machine by sending a malformed packet to the DCOM service.
Your Windows needs urgent update...

[Invocation]

Do you use a firewall? Which one?

The other thing is that mainly today but also yesterday I started getting this pop-up from avast at the bottom of my screen in red, blue and yellow:DCOM Exploit keeps being blocked. Attack from 81.178.227.238.174 or 175 (it changes) tcp

It's strange but seems you don't have a firewall.

Messages like: Network Shield: blocked "DCOM Exploit" - attack from 81.178.115.162:135/tcp
are due to the RPC/DCOM exploit, which is a vulnerability that allows an attacker to gain access to the destination machine by sending a malformed packet to the DCOM service.
Your Windows needs urgent update...

Thanks for ALL the information spread across this thread. I've tried to do some sort of meta-analysis of what everyone has said that I understand and feel capable of doing. To answer your first question I do have a firewall although I may not have it configured correctly and if anyone could help me do so I would be very grateful. I'm using GesWall.

I've just installed IE Service Pack 4 (it's IE 5 I've got installed currently) and used Windows Update to perform urgent updates but "DCOM Exploit" is still bothering me although the pop-up doesn't seem as frequent as it was. I also just tried to install IE6 with the one of the setup d/l's I had in a folder and it appeared to install without problem but apparently you can find out what copy of IE you've got by going to the Start menu->Run->type winver and hit ok. When I did this is it told me I still had version 5 with service pack 4, so god knows?

Mind you, now I've installed SP4 or updated windows (I don't know why) I have been able to install Firefox successfully.

But what do I do to get rid of this bloody "DCOM Exploit" thing now?

[Eddy]

Messages like: Network Shield: blocked "DCOM Exploit" - attack from 81.178.115.162:135/tcp

It is just a msg from the avasat network shield, you can change the settings in avast's settings if you don't want to see it.

now I've installed SP4 or updated windows (I don't know why) I have been able to install Firefox successfully.

What exact version of Windows are you using?

What other security do you have running/installed?
Are you using a router?

[Invocation]

I seem to have found an acceptable answer via a post I read on this very forum somewhere after following a link after Googling 'DCOM Exploit'. You need to go here http://www.grc.com/freehistorical.htm and d/l the DCOMBobulator. It doesn't seem to stop all the pop-ups necessarily but I'm getting very few now (although I have just installed loads of 'urgent' Microsoft Updates too) and at least your pc is safe from attacks getting through.

Ever since Windows 98, a powerful, but unnecessary and rarely used facility known as DCOM (Distributed Component Object Model) has been an integral part of Windows. The DCOMbobulator checks the effectiveness of Microsoft's security patches and allows the user to increase the security of their system by simply turning DCOM off.

Easy when you know how eh? 

[Invocation]

....double post

[DavidR]

By disabling the DCOM function protects you from the exploit should it get past avast, what it won't do is stop people/infected systems trying to infect your system. They don't know if you are vulnerable or not, they just try it on.

The only way to stop the attempts t to ensure your system is stealthed (hidden) to the internet, if they can't see you they can't attack you and for that you need a firewall, which should hide your system or filter the attempt and avast's Network Shield won't have to alert you. Or as Eddy said disable the alerts in Network Shield and just have it block them. However, Network Shield isn't a full blown firewall so you would be vulnerable in other areas, so a firewall is essential.