C:\Program Files\Common Files\Symantec Shared\VirusDefs folder takes more than 1.58 GB .

are there tmpXXXX.tmp files under this folder?

If yes, can you check the steps

http://www.symantec.com/business/support/index?page=content&id=TECH102927

also check

Configuring the number of content revisions kept by the Symantec Endpoint Protection (SEP) client 11.x

http://www.symantec.com/business/support/index?page=content&id=TECH103956

you can delete all the old date definition..

Hello,

Configure the Disk space Management for Virus Def.

To configure the disk space used for LiveUpdate downloads

1. In the console, click Admin.

2. Click Servers and select the site that you want to configure.

3. Under Tasks, click Edit Site Properties, and then click LiveUpdate.

4. Under Disk Space Management for Downloads, type the number of content downloads that you want to store.

5. If you want to reduce the amount of disk space used, uncheck the Store client packages unzipped to provide better network performance for upgrades option. Note: Disabling this option also disables the ability of Symantec Endpoint Protection Manager to construct deltas between content revisions and may adversely affect network performance for updates.

6. Click OK.

Disk Space Management procedures for the Symantec Endpoint Protection Manager

http://www.symantec.com/docs/TECH96214

Drive Space used by Virus Definitions Updates

http://www.symantec.com/docs/TECH141811

What is the version of the product?

Is it Symantec Antivirus 10.x, Symantec Endpoint Protection 11.x or 12.1?

kindly update the latest status of your issue?

• Symantec Endpoint Protection 11.x will keep 3 definition sets at any time: the current set and the last 2.
• Symantec Antivirus  8.x/9.x/10.x will keep 2 definition sets: the current set and the last used.
• Symantec End Point Protection 12.1.x will keep 1 set of definations.

If you see more defination being stored..... that would be cause the definations are corrupted.

I would suggest you to stop the smc services of the client and delete the definations and then monitor the issue. I am sure this would help.

From this locaiton  that you have provided about virus defs.... >> C:\Program Files\Common Files\Symantec Shared\VirusDefs

This is the locaiton for 11.0.x client.

You could also refer to below article

Drive Space used by Virus Definitions Updates

Article URL http://www.symantec.com/docs/TECH141811