Hello kodl and welcome to the forum,
While no software is 100%, I need more information about your system to assist you and answer your question.
1. What is your OS, 32 or 64-bit?
2. What version of Avast did you install? 5.0.677?
3. What product of Avast did you install? Free, Pro, AIS?
4. What other security software do you currently have or did you have in the past on this machine including:
- Antivirus (AV)
- Firewall (FW)
- Trial versions of AV, FW and other security programs
- Other security software
5. Are your MS Updates and software up to date?
6. Are you using genuine Windows and genuine (non-pirated) software?
7. Are your Avast definitions up to date?
8. When you discovered the problem, did you try doing a scan with Avast? If so, what type of scan(s)?
Was your machine acting strange that prompted you to check for malware? If so, how long has it been acting strange? If not, what were you doing when you first discovered something was wrong?
How did you check ("third-party removal tools") for the malware?
Did you quarantine or delete the malware?
Yes, malware that has been around for years can still infect you...especially depending on your answers to the above questions. Malware is also changing (mutating), and antivirus detection therefore has to change as well to detect it, so this malware you got may have been a mutated version. Without more information, I cannot give you that answer.
