Until 2 weeks ago we had a fully functional wired network, based around a Windows NT4 server. Most of our PC’s are NT4 (SP6), some Win2K, some WinXP, and a couple of Windows 98, all of them well patched. All could access the server and the Internet 100%, while Microsoft Exchange Server 5.5 handled our email system perfectly. Internet access was ISDN via a router.
We upgraded the Internet system to 1Mb cable broadband, i.e. the existing ISDN telephone line was replaced by a 1Mb cabled system, with new Motorola modem and a Netgear RP614v2 router to replace the existing Netopia router. It took about 2 days to get all the stuff organised, including a changeover of ISP, etc. Initially everything went according to plan, but then an intermittent problem appeared, which took a couple of days to correctly identify.
About a minute after connecting a rogue (Windows 2000 Pro) laptop to our network, it invariably causes the Internet connection to drop (and email to cease) for everyone. Similarly, about a minute after unplugging it from the network, access resumes. Strangely enough, it’s possible to continually ping out to an external IP address from anywhere on the network, even when the connection is dropped.
The laptop (a Sony Vaio PCG873M) is occasionally used outside the office to connect to the internet via a dial-up connection. Some weeks ago, after being carelessly used with some P2P file sharing system, it was infected by virus ‘W32/Sdbot.worm.gen.j’, ‘W32/Gaobot.worm.gen.f’ and other stuff. There is evidence of “Back Orifice B” and “Cydoor”, but all have definitely now been removed. I’ve used McAfee, Adaware SE, Hijack This, Spybot S&D, CWS shredder, etc to remove any obvious malware.
The modem and router have both been check and replaced. The incoming line has been checked. Restarting the router solves the problem for about a minute, and then the connection drops (for everyone) again. I uninstalled and reinstalled TCP/IP on the rogue laptop but no improvement. Programs installed on it include McAfee AV, MS Office 2000, AutooCAD LT2002, ACDSee, etc.
I would greatly appreciate any further suggestions, preferably avoiding a complete reinstall.
We upgraded the Internet system to 1Mb cable broadband, i.e. the existing ISDN telephone line was replaced by a 1Mb cabled system, with new Motorola modem and a Netgear RP614v2 router to replace the existing Netopia router. It took about 2 days to get all the stuff organised, including a changeover of ISP, etc. Initially everything went according to plan, but then an intermittent problem appeared, which took a couple of days to correctly identify.
About a minute after connecting a rogue (Windows 2000 Pro) laptop to our network, it invariably causes the Internet connection to drop (and email to cease) for everyone. Similarly, about a minute after unplugging it from the network, access resumes. Strangely enough, it’s possible to continually ping out to an external IP address from anywhere on the network, even when the connection is dropped.
The laptop (a Sony Vaio PCG873M) is occasionally used outside the office to connect to the internet via a dial-up connection. Some weeks ago, after being carelessly used with some P2P file sharing system, it was infected by virus ‘W32/Sdbot.worm.gen.j’, ‘W32/Gaobot.worm.gen.f’ and other stuff. There is evidence of “Back Orifice B” and “Cydoor”, but all have definitely now been removed. I’ve used McAfee, Adaware SE, Hijack This, Spybot S&D, CWS shredder, etc to remove any obvious malware.
The modem and router have both been check and replaced. The incoming line has been checked. Restarting the router solves the problem for about a minute, and then the connection drops (for everyone) again. I uninstalled and reinstalled TCP/IP on the rogue laptop but no improvement. Programs installed on it include McAfee AV, MS Office 2000, AutooCAD LT2002, ACDSee, etc.
I would greatly appreciate any further suggestions, preferably avoiding a complete reinstall.
