Threat not found by Avast

[frampo]

I have a number of machines running different av programs.
My main computer runs Avast pro and my work laptop runs NOD32.
NOD32 has detected the following threat embedded in spam in my hotmail account, but Avast does not.
Why does Avast not detect this?

Regards
Dan

Threat = JS/redir.AH trojan

JS.Redir.ah
JS.Redir.ah Threat Level: 
 
Alias: JS.Redir.ah,JS_REDIR.AH Platforms: Win 95,Win 98,Win ME,Win NT,Win 2K,Win XP
Updated on: 11 December, 2006
Arrival Form:  Email
Type: Win32,Trojan,JavaScript
Damage: Other
 
 
Analysis
JS.Redir.ah is a malicious JavaScript that is usually embedded in an HTML page that arrives on a system as an attachment to a spammed email message.

Once the recipient opens the attachment, this script loads the web page http://{BLOCKED}ghtBooksDirect.info/?b40eF7ce8fc50T34b5400d5593Bf11ea. The said web page contains another malicious JavaScript.

[Lisandro]

To know if a file is a false positive or it's infected, please submit it to JOTTI or VirusTotal and let us know the result. Thenve, send it in a password protected zip to virus@avast.com
Please, mention in the body a link to this thread and the password used. Thanks.

[frampo]

Email sent.

Dan

[Lisandro]

Email sent.

Thanks Dan for helping improving avast detection.

[frampo]

your most welcome.