百度搜索、百度贴吧等都无法使用，用百度搜索的时候却出来sogou的搜索结果，很多网站都无法登录（包括一些杀毒网站）经查看，发现c盘windows/system32/drivers/etc下的hosts文件已经被修改成以下所示：
127.0.0.1
localhost
219.235.3.16
search.114.vnet.cn
219.235.3.16
keyword.vnet.cn
..........................
（由于字数所限，这里的大部分内容已被省略）
而此文件原为：
# Copyright (c) 1993-1999 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
#
102.54.94.97
rhino.acme.com
# source server
#
38.25.63.10
x.acme.com
# x client host
127.0.0.1
localhost
经验证,在被恶意修改后的hosts文件中所列的网站全部被屏蔽无法访问,想把它修改回去，却显示文件正在被使用而无法修改。用最新版的杀毒软件进行查杀也没有发现病毒，请问这是什么病毒？
