I don't know where the request for keepalive.aspx would be coming from, the keepalive task doesn't call it as far as I know.
If you look in global.asax.cs Application_Start is where this task is queued, and its configured to call the site root not keepalive.aspx
AppKeepAliveTask keepAlive = new AppKeepAliveTask();
keepAlive.UrlToRequest = WebUtils.GetSiteRoot();
keepAlive.MaxRunTimeMinutes = 720; //12 hours
keepAlive.MinutesToSleep = 10;
I often see strange requests in my log that are just scripts poking at my site. For example I sometime see requests for DesktopDefault.aspx which is not a file that exists in mojoportal, but does exist in rainbow portal.