wordpress site infected by JS:redirector-boj trj

Dear madam, sir,
I am the admnistrator of our school website : www.ecolejeannedarc-lamadeleine.fr which on CMS wordpress
Since few days we can not access to it anymore, the following avast warning appears : JS:Redirector-boj trj
Can anyone help me to identify where the malware is on our website and how I can remove it ?

Many thanks !

website is infected. http://sitecheck.sucuri.net/results/www.ecolejeannedarc-lamadeleine.fr

Malware entry: MW:JS:IFRAME:DOCUMENT-WRITE3
http://labs.sucuri.net/db/malware/mwjs-iframe-document-write3?v7

VirusTotal
https://www.virustotal.com/en/file/2938467e7ff67d8a7e20f3710ced27351e0de54dd562584fe8a18c11eec5a325/analysis/1390976723/

unmaskparasites: http://www.UnmaskParasites.com/security-report/?page=www.ecolejeannedarc-lamadeleine.fr

urlQuery http://urlquery.net/queued.php?id=62910623

Your IP adress 195.144.11.40 is on one blacklist here http://whatismyipaddress.com/blacklist-check

thank you, at least I now know what is wrong. Do you have any idea on how I can get rid of them ?
many thanks !

I will PM one that may be able to help you…it may take some time before he is online

Sucuri can help…but it is not free http://sucuri.net/signup