Yahoo!mail infetta? - Email si replica a tutta la rubrica

Salve a tutti,
Questa mattina apro la mia casella di posta du yahoo e trovo nella posta in arrivo ben 3 email che come oggetto avevano il classico "failure notice" e come mittente "****Canc by Keko****".

Apro la prima delle emil e il testo è il seguente:
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Hi. This is the qmail-send program at yahoo.com.
I'm afraid I wasn't able to deliver your message to the following addresses.
This is a permanent error; I've given up. Sorry it didn't work out.

****Canc by Keko****
77.238.177.9 failed after I sent the message.
Remote host said: 554 delivery error: dd Sorry your message to ****Canc by Keko**** cannot be delivered. This account has been disabled or discontinued [#102]. - ****Canc by Keko****

****Canc by Keko****
62.211.72.32 does not like recipient.
Remote host said: 550 RCPT TO:<****Canc by Keko****> User unknown
Giving up on 62.211.72.32.

--- Below this line is a copy of the message.

Return-Path: <****Canc by Keko****>
Received: (qmail 25896 invoked by uid 60001); 18 Sep 2010 01:46:04 -0000
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.it; s=s1024; t=1284774364; bh=Jz7jcXPwcmthUsysz63hlnjwsgQAiVTd6T3RSaA1e9w=; h=Message-ID:X-YMail-OSG:Received:X-Mailerate:From:Subject:To:MIME-Version:Content-Type; b=mfjmOB3/zzu/1W+tzR65ZXa83bc1ahZlE072mqbvJhwCoa2Ydt4+qfsDpghU1+mJQtf+wNq9K6jQYOqQjM0Gf77h7lMe1CmMO/wICbOPJrndWe2g+sItJzRWb75ixxnE0pd1nsgRAMG3bEvuaABnC+PGmj267iirjobZ+5F8JT4=
DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws;
s=s1024; d=yahoo.it;
h=Message-ID:X-YMail-OSG:Received:X-Mailerate:From:Subject:To:MIME-Version:Content-Type;
b=HwQ8kXbH+Ler+QRNVdh7p0WHCqIvKDMuh4xZv3AmtxHKrJWHGhnjgOfpTKWxHU/5RhG8ocVKC/tPO9JqXkab5To9YWF6TOyGZQtQ5fff9Nz5EhzT5BQq2s9xUqO5gWVS0DEVTvdENoa+HvRtL9xDJvX9jH/Mg7UFpcAAcIgXwQ0=;
Message-ID: <****Canc by Keko****>
X-YMail-OSG: 1EznK_oVM1kSewvOE_mCPQHmTUrzut9fsI7mjlvZ46EvRPj
nyc3OAg2zZYxtXIItJfEgtmjKgm_RpENs560QmKdqlUwD3LT8.AxYvNfXYLx
VLI9SbnekM7tMcZXnFXLXXKKabcfSSBdOvlyModPOe3yvZObDAdpC0eDcD57
O2yIuust0pYagCuVPbekIYgsU1WPsqDcfs9jSn.X_Jy4TuEv2MIDyWfz5DGq
O0Anpbd3YVxb6oHIpTjwZEG9sd0iOyknXVolMwJTdU9hPU_i2czA6H_tUek_
MVGiXkq07p4an0jMkeVjHvOmMtJ8XkRjO5pXJFJNWVk7gwpNhMKSt7tvS
Received: from [123.11.69.207] by ****Canc by Keko**** via HTTP; Sat, 18 Sep 2010 01:46:01 GMT
X-Mailer: YahooMailClassic/11.4.9 YahooMailWebService/0.8.105.279950
Date: Sat, 18 Sep 2010 01:46:01 +0000 (GMT)
From: =?iso-8859-1?Q?=AF=60=B7=2E=B8=B8=2E-=3E_reditutto_=3C-=2E=B8=B8=2E=B7=B4?= =?iso-8859-1?Q?=AF?= <****Canc by Keko****>
Subject: Dear friend ! 9
To: ****Canc by Keko****
MIME-Version: 1.0
Content-Type: multipart/alternative; boundary="0-1528731543-1284774361=:22636"

--0-1528731543-1284774361=:22636
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: quoted-printable

I have a Japanese friend told me that he worked in a Japanese company. I vi=
sited the company he worked for and found the products very favorable. And =
there are many product versions, such as the European version, American ver=
sion, and the Asian version and so on. All company's products take photos f=
or the true products. I suggest you should have a look in this website. The=
re is the company website :http://www.wto-business.com , You can enjoy a lo=
t of benefits in the second shopping time. Thank you ! n=0A=0A=0A
--0-1528731543-1284774361=:22636
Content-Type: text/html; charset=iso-8859-1
Content-Transfer-Encoding: quoted-printable

<table cellspacing=3D"0" cellpadding=3D"0" border=3D"0" ><tr><td valign=3D"=
top" style=3D"font: inherit;">I have a Japanese friend told me that he work=
ed in a Japanese company. I visited the company he worked for and found the=
products very favorable. And there are many product versions, such as the =
European version, American version, and the Asian version and so on. All co=
mpany's products take photos for the true products. I suggest you should ha=
ve a look in this website. There is the company website :<A href=3D"http://=
Wto-business.com">http://www.wto-business.com</A> , You can enjoy a lot=
of benefits in the second shopping time. Thank you ! n</td></tr></table><b=
r>=0A=0A=0A=0A
--0-1528731543-1284774361=:22636--

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Le altre 2 email in arrivo sono identiche.
guardo la cartella posta inviata e noto che questa email s'è replicata a tutta la rubrica per 3 volte.
Ora vi chiedo quale può essere il problema, a cosa vado incontro e quali sono i rimedi.
Intanto sto lanciando il mio fidato SpyBot (aggiornato), ho già programmato la scansione all'avvio del mio Avast!.
Non uso altri strumenti per la manutenzione del PC.

Accetto suggerimenti,
Grazie Mille!!