Sex trafficking
Sex trafficking is human trafficking for the purpose of sexual exploitation, including sexual slavery. A victim is forced, in one of a variety of ways, into a situation of dependency on their trafficker(s) and then used by said trafficker(s) to give sexual services to customers. There are three types of activities defined as sex trafficking crimes: acquisition, transportation and exploitation; this includes child sex tourism (CST), domestic minor sex trafficking (DMST) or other kinds of commercial sexual exploitation of children, and prostitution. Sex trafficking is one of the biggest criminal businesses and it has been described as "the fastest growing criminal industry in the world."
Trafficking of children
The Optional Protocol on the Sale of Children, Child Prostitution and Child Pornography is a protocol of the Convention on the Rights of the Child, formally adopted by the United Nations in 2000. Essentially, this protocol formally requires states to prohibit the sale of children, child prostitution, and child pornography. According to the International Labour Organization, sexual exploitation of children includes all of the following practices and activities: 
Though measuring the extent of this practice is difficult due to its criminal and covert nature, the International Labour Organization estimates that there are as many as 1.8 million children sexually trafficked worldwide, while UNICEF's 2006 State of the World's Children Report reports this number to be 2 million. The International Labour Organization has found that girls involved in other forms of child labour - such as domestic service or street vending - are at the highest risk of being pulled into commercial child sex trafficking. Likewise, Kendall and Funk justifies how “young girls age 12 and under are malleable and more easily trained into their prospective roles as prostitutes, and because virginity is highly prized by certain consumers willing to pay a premium” (31).A variety of sources, including the I.L.O, and scholars Erin Kunze and D.M. Hughes, also contend that the increased use and availability of the Internet has served as a major resource for traffickers, ultimately increasing the incidence of child sex trafficking. In fact, in 2009, Illinois Sheriff Thomas J. Dart sued the owners of Craigslist, a popular online classifieds website, for its "allowance" and "facilitation" of prostitution, particularly in children. In response to public and legal pressure, Craigslist has since blocked all access to its "Adult Services" section.