Antivirus...Full Capabilities Offline

Other than for updates and real-time, which antivirus' have full scan and removal capabilities offline?

I been using Avast Free for some time now and throughout the whole time I occasionally receive the message..."UI cannot connect". I used AVG by Grisoft before Avast acquired it and it never had the User Interface connection error.

IMHO, nobody anywhere should ever see a message like this from whatever security software they use. The user should be able to perform a full system scan offline, but with Avast Free Antivirus apparently the user needs connection to even open the Avast.

A lot of anti-virus software has gone cloud-based to keep up with the overwhelming amount of virus definitions, thus it needs an Internet connection. You could try Bitdefender Free. It may work better.

Or look at something else like Faronics Anti-executable or Shadow Defender.

Any sane antivirus program would never require internet connection for operating, ever. Updates are the only exception to this, certainly having a need for internet connection, totally understandable. Other than that, nothing requires an internet connection.
Real time scanning is done by infecting your system with kernel drivers that intercept every file operation and pass though the antivirus engine, but of course the network is not involved at all.
A good usage of internet could be submiting doubtful samples for analyzing by their people, an action that always should be explicitly authorized by the user, but other than providing material for future definitions, it's not required for normal operation.

From here we could only guess. Avast is famous for showing spam to the user, and may "require" internet access to download unwanted ads. Many antiviruses with free and commercial versions use this bad practice on their freebies. Another idea is that they use some form of "license check", a questionable practice that verifies only if you're "authorized" to use the software, sometimes inflicted upon the free versions. A more far-fetched, but still possible scenario is that the antivirus includes some spyware and is stealing private data from you.
While none of those are really required, and are against the user's best interest, software may be designed to cease to function if the internet connection required for all of those is interupted. Of course, that's only my speculation, backed only by my personal experience and knowledge, but not by hard proof against any particular antivirus, so take those with a grain of salt.

F22 Simpilot said:

A lot of anti-virus software has gone cloud-based to keep up with the overwhelming amount of virus definitions, thus it needs an Internet connection. You could try Bitdefender Free. It may work better.

What everyone has failed to explain is what's that "cloud-based" thing is all about. What they say simply don't make any sense when put in the real world. Many definitions are easy to deal with, simply issue more frequent updates. But the scanning process itself has always, since day one and up to this day, ran locally, since "the cloud" has no idea what's happening in my computer.

The definitions come from the cloud to keep up with polymorphic malware. You're better off with a sandboxed OS.

WyattWhiteEagle said:

Other than for updates and real-time, which antivirus' have full scan and removal capabilities offline?

I been using Avast Free for some time now and throughout the whole time I occasionally receive the message..."UI cannot connect". I used AVG by Grisoft before Avast acquired it and it never had the User Interface connection error.

IMHO, nobody anywhere should ever see a message like this from whatever security software they use. The user should be able to perform a full system scan offline, but with Avast Free Antivirus apparently the user needs connection to even open the Avast.

With the Avast, had you gone into Settings > Update and changed both Program and Virus Definitions to Manual Update?

Another suggestion I can think of, is to run the MRT.exe (Microsoft Removal Tool) that you get once a month via Windows Update. That tool can perform full scans offline.