各位大哥，这种攻击模式能避免吗？

asus1024

因邮件服务器放在内网，所以看到的来源IP都是内网的。这样的情况能避免恶意的猜测密码吗？

Nov 30 12:12:11 mail vpopmail[17551]: vchkpw-pop3: password fail danny@ast123.com:172.16.0.1
Nov 30 12:12:11 mail vpopmail[17553]: vchkpw-pop3: vpopmail user not found alpha@ast123.com:172.16.0.1
Nov 30 12:12:11 mail vpopmail[17555]: vchkpw-pop3: vpopmail user not found summer@ast123.com:172.16.0.1
Nov 30 12:12:11 mail vpopmail[17557]: vchkpw-pop3: vpopmail user not found david@ast123.com:172.16.0.1
Nov 30 12:12:11 mail vpopmail[17560]: vchkpw-pop3: vpopmail user not found guest@ast123.com:172.16.0.1
Nov 30 12:12:11 mail vpopmail[17562]: vchkpw-pop3: vpopmail user not found mike@ast123.com:172.16.0.1
Nov 30 12:12:11 mail vpopmail[17564]: vchkpw-pop3: vpopmail user not found james@ast123.com:172.16.0.1
Nov 30 12:12:12 mail vpopmail[17568]: vchkpw-pop3: vpopmail user not found jennifer@ast123.com:172.16.0.1
Nov 30 12:12:12 mail vpopmail[17570]: vchkpw-pop3: vpopmail user not found testing@ast123.com:172.16.0.1
Nov 30 12:12:12 mail vpopmail[17577]: vchkpw-pop3: vpopmail user not found office@ast123.com:172.16.0.1
Nov 30 12:12:12 mail vpopmail[17579]: vchkpw-pop3: vpopmail user not found justin@ast123.com:172.16.0.1
Nov 30 12:12:12 mail vpopmail[17581]: vchkpw-pop3: vpopmail user not found cindy@ast123.com:172.16.0.1
Nov 30 12:12:12 mail vpopmail[17584]: vchkpw-pop3: vpopmail user not found michael@ast123.com:172.16.0.1
Nov 30 12:12:12 mail vpopmail[17586]: vchkpw-pop3: vpopmail user not found guest@ast123.com:172.16.0.1
Nov 30 12:12:12 mail vpopmail[17589]: vchkpw-pop3: vpopmail user not found alpha@ast123.com:172.16.0.1
Nov 30 12:12:13 mail vpopmail[17591]: vchkpw-pop3: vpopmail user not found summer@ast123.com:172.16.0.1
Nov 30 12:12:13 mail vpopmail[17593]: vchkpw-pop3: vpopmail user not found mike@ast123.com:172.16.0.1
Nov 30 12:12:13 mail vpopmail[17596]: vchkpw-pop3: vpopmail user not found james@ast123.com:172.16.0.1
Nov 30 12:12:13 mail vpopmail[17599]: vchkpw-pop3: vpopmail user not found jennifer@ast123.com:172.16.0.1
Nov 30 12:12:13 mail vpopmail[17602]: vchkpw-pop3: vpopmail user not found testing@ast123.com:172.16.0.1
Nov 30 12:12:13 mail vpopmail[17607]: vchkpw-pop3: vpopmail user not found justin@ast123.com:172.16.0.1
Nov 30 12:12:14 mail vpopmail[17610]: vchkpw-pop3: vpopmail user not found office@ast123.com:172.16.0.1
Nov 30 12:12:14 mail vpopmail[17611]: vchkpw-pop3: vpopmail user not found cindy@ast123.com:172.16.0.1
Nov 30 12:12:14 mail vpopmail[17615]: vchkpw-pop3: vpopmail user not found guest@ast123.com:172.16.0.1
Nov 30 12:12:14 mail vpopmail[17617]: vchkpw-pop3: vpopmail user not found james@ast123.com:172.16.0.1
Nov 30 12:12:14 mail vpopmail[17620]: vchkpw-pop3: vpopmail user not found alpha@ast123.com:172.16.0.1
Nov 30 12:12:14 mail vpopmail[17622]: vchkpw-pop3: vpopmail user not found testing@ast123.com:172.16.0.1
Nov 30 12:12:15 mail vpopmail[17626]: vchkpw-pop3: vpopmail user not found justin@ast123.com:172.16.0.1
Nov 30 12:12:15 mail vpopmail[17628]: vchkpw-pop3: vpopmail user not found mike@ast123.com:172.16.0.1
Nov 30 12:12:15 mail vpopmail[17631]: vchkpw-pop3: vpopmail user not found cindy@ast123.com:172.16.0.1
Nov 30 12:12:15 mail vpopmail[17633]: vchkpw-pop3: vpopmail user not found guest@ast123.com:172.16.0.1
Nov 30 12:12:15 mail vpopmail[17635]: vchkpw-pop3: vpopmail user not found alpha@ast123.com:172.16.0.1
Nov 30 12:12:16 mail vpopmail[17639]: vchkpw-pop3: vpopmail user not found mike@ast123.com:172.16.0.1
Nov 30 12:12:16 mail vpopmail[17641]: vchkpw-pop3: vpopmail user not found cindy@ast123.com:172.16.0.1
Nov 30 12:12:17 mail vpopmail[17644]: vchkpw-pop3: vpopmail user not found cindy@ast123.com:172.16.0.1
Nov 30 12:12:19 mail vpopmail[17647]: vchkpw-pop3: vpopmail user not found cindy@ast123.com:172.16.0.1

刘五十三

怀疑是中了木马吧，内网猜到了密码有什么用？说不定那个家伙下载了什么黑客软件在运行。

ruochen

干掉连接的ip