Suddenly cannot access any Microsoft web site

[jimn]

I hadn't tried to access Microsoft's update site for a while. I let there biggie of 2 Tuesdays ago settle in first.
Sunday I went to do updates using the IE6 "Tools" option for "Windows update" and it came back as "Page not found". Same thing for ANY Microsoft site. Win XP Pro SP2. Tried my 2 other machines and SAME RESULT!!! (1 Win2K and 1 WinXP/SP1)

I've re-booted DSL modem and the router.
I've checked HOSTS and nothing wrong in there (only the original in it).
I've tried PINGing and get no where.
I've called my ISP and accused them of blocking me. They said they don't, ever.
I've reset the MTU (PC) with no joy.
I've stopped Windows firewall. No Joy.
I didn't see anything untoward in the router's various settings.

My last chance is Avast! itself, since it's on all 3 systems.
Can it be?... Or any ideas?

[DavidR]

I doubt that avast has anything to do with this problem.

Unless you put Microsoft.com in the web shield, Customized, URL Blocking there is no reason why avast would block it as it isn't a firewall. If this had been all of the web then I would have said it could be a firewall blocking the web shield provider, however, since it only effects Microsoft I can't see it being that.

All I can suggest is checking the Security Settings in IE and see if it is somehow blocked, it (windows update) should really be in the Trusted Zone of the security settings.

If you haven't already got this software (freeware), download, install, update and run it, preferably in safe mode Ewido Security Suite.
Also if you haven't got these.
1. Ad-Aware
2. Spybot Search and Destroy
3. Spywareblaster Don't install this until you are clean.


There is some malware that tries to block windows update for obvious reasons

You also need a proper firewall and XP's isn't up to the job. Zone Alarm free http://www.zonelabs.com works fine with avast and has a reasonably friendly user interface. There are others, Comodo, Jetico, Sunbelt Kerio, etc.
See some firewall tests for comparison, some are freeware but many are paid for versions http://www.firewallleaktester.com/tests.php. Also see http://www.thefreecountry.com/security/firewalls.shtml
Any malware that manages to get past your defences will have free reign to connect to the internet to either download more of the same, pass your personal data (user names, passwords, keylogger retrieved data, etc.) or open a backdoor to your computer, so outbound protection is essential.

[jimn]

I forgot to mention that I had also run SpyBot.
It found some on 2 machines, but nothing on the third (the one I use infrequently).

My problem is that I don't know where to look. I tried Google, and one item looked promising, but it was on a Microsoft site@!#@#!@#

By the way, I had also tried changing an IE (6) setting to always check for IE updates on startup. That also got me a "Page not found".

Thanks for the words. I just don't see doing anything more about firewall at this time because it doesn't seem implicated (same result on Win2K).
Maybe I'll disable the firewall on the router...

[DavidR]

If you have malware on your system that could be responsible for this then it has unfettered access to the internet to potentially do what it likes. So I feel you should close the outbound door, which may alert you to anything unauthorised outbound connections. I wouldn't have though the router firewall was an issue as that too is almost certainly only covering inbound connections.

Changing the settings to check for updates work until the block is overcome, is windows update in the trusted sites zone in IE security ?

Have you tried Ewido in safe mode as suggested ?

I'm at a loss as to what it might be that is blocking access to Microsoft.com (and not other sites, like AV sites, all the web, etc.) if you have checked the Hosts file and IE security settings.
Although you can update using a different browser but can you connect to Microsoft.com using firefox/opera, etc. This would confirm if it is across the board or just effecting IE.

[jimn]

I made this weekend the date that I would get this fixed, and finally it is.

The cause, to me, is UNBELIEVABLE, yet it is true!!!
My Googling had found a few messages suggesting that the "MTU" value required changing, so using DrTCP I had changed it to 1492, 1480 and 1468, all with no joy.

It turns out that the cause was the MTU value, but it needed to be set somewhere in the 1400 range. Finding that 1400 did get me access to Microsoft sites, i tried other values and the max I could get was 1440.
The ISP, since my initial call 10+ days ago, seems to have had several more calls from other people, naming a handful of other sites. Yet I still had go go the 'get the router out of the way' route before they would entertain other options!@#@!
Seems they had upgraded some key equipment the day before I first found the problem but no one connected the 2 events. Even as of today the "MTU" was their best ***guess*** and the guy was quite surprised when I told him I got in to Microsoft.

I hope this helps anyone who encounters a similar problem.

Thanks to everyone who took a shot. Your advices were helpful in other ways, regardless.