Well I would urgently check with your Hosting Company for a start.

I have, and here's what they said:

Dear Charles LePage,

Sorry to hear that. I have just checked with the data centre, our engineers have found out aparently some IPs were attacking your site by manipulating your php files which were about to cause a denial of service on the server. Fortunately, our monitoring software deployed on the server had removed the associated files otherwise the hard disk would have been filled up by error log files (close to 60GB at the time) with entries similar to the followings:

[Tue Dec 12 04:40:12 2006] [error] PHP Notice: Undefined property: pingback_url in /home/comlist/public_html/inc
/MODEL/dataobjects/_dataobject.class.php on line 461
[Tue Dec 12 04:40:12 2006] [error] PHP Notice: Undefined variable: blog in /home/comlist/public_html/plugins/_si
deblog.plugin.php on line 114
[Tue Dec 12 04:40:12 2006] [error] PHP Notice: Undefined variable: show_statuses in /home/comlist/public_html/pl
ugins/_sideblog.plugin.php on line 136
[Tue Dec 12 04:40:12 2006] [error] PHP Notice: Undefined variable: m in /home/comlist/public_html/plugins/_sideb
log.plugin.php on line 136
[Tue Dec 12 04:40:12 2006] [error] PHP Notice: Undefined variable: w in /home/comlist/public_html/plugins/_sideb
log.plugin.php on line 136
[Tue Dec 12 04:40:12 2006] [error] PHP Notice: Undefined variable: author in /home/comlist/public_html/plugins/_
sideblog.plugin.php on line 136
[Tue Dec 12 04:40:12 2006] [error] PHP Notice: Undefined variable: orderby in /home/comlist/public_html/plugins/
_sideblog.plugin.php on line 136
[Tue Dec 12 04:40:12 2006] [error] PHP Notice: Undefined variable: unit in /home/comlist/public_html/plugins/_si
deblog.plugin.php on line 136
[Tue Dec 12 04:40:12 2006] [error] PHP Notice: Undefined variable: timestamp_min in /home/comlist/public_html/pl
ugins/_sideblog.plugin.php on line 136
[Tue Dec 12 04:40:12 2006] [error] PHP Notice: Undefined variable: timestamp_max in /home/comlist/public_html/pl
ugins/_sideblog.plugin.php on line 136
[Tue Dec 12 04:40:12 2006] [error] PHP Notice: Undefined index: display in /home/comlist/public_html/plugins/dem
ocracy_plugin/_democracy.plugin.php on line 418

What version were you running? More to the point, did you upgrade after the very recent security vulnerability was discovered? It's possible that someone was trying to exploit the problem, but it's hard to say for sure. Your version number can be found in conf/_application.php as $app_version.

I'm running "$app_version = '1.9.1-beta';"

The quoted entries from the error log are "normal" notices, caused by undefined vars in the code.
That's not critical and has nothing to do with "some IPs were attacking your site by manipulating your php files".

You should add

ini_set( 'error_reporting', E_ALL & ~E_NOTICE );

to /conf/_basic_config.php - though b2evo should be "notices-free", but some plugins and "/inc/MODEL/dataobjects/_dataobject.class.php on line 461" are not - obviously.

The notice in _dataobject.class.php means that you're using $Blog->get('pingback_url') somewhere, but it has been removed in 1.9.1 - so it's OK to have a notice here. The other notices happen because the plugin authors have not enabled displaying notices while developping the plugin and therefor missed them.

blueyed wrote:

The quoted entries from the error log are "normal" notices, caused by undefined vars in the code.
That's not critical and has nothing to do with "some IPs were attacking your site by manipulating your php files".

You should add

ini_set( 'error_reporting', E_ALL & ~E_NOTICE );

to /conf/_basic_config.php - though b2evo should be "notices-free", but some plugins and "/inc/MODEL/dataobjects/_dataobject.class.php on line 461" are not - obviously.

I wonder why I suddenly had so many of those errors.

I've added the suggested code, and I thank you!