Exploit:Win32/Evenex.gen is a generic detection for malware, which exploit a vulnerability in a specially crafted Excel document that may corrupt system memory allowing the attacker to execute arbitrary code.
In order for this attack to be carried out, a user must first open a specially crafted Excel file attached to an e-mail or otherwise provided to them by an attacker. If a user opens the malicious Excel document using a vulnerable computer, the exploit could execute arbitrary code which could include any number of actions such as downloading or installing other malware.
An attacker who successfully exploited this vulnerability could run arbitrary code as the currently logged-on user.
There are no common symptoms associated with this threat. Alert notifications from installed antivirus software may be the only symptom(s).