Posing and masquerading
It is easier to use online communication to pretend to be someone that you are not. Society has for centuries needed to deal with the problem of people pretending to be physicians, priests, policemen, or unmarried men. But it has required considerable skill as an actor to succeed at such deception. It seems to be more common for people on the internet to pose as something that they are not. Even law enforcement authorities do it. Newspapers carry stories of policemen pretending to be teenage girls, hoping to apprehend for prosecution people pretending to be virtuous teenage boys; the search of any large news archive will yield stories of arrests of adults propositioning someone they thought to be a minor. There is room for moral authorities to take an educated stand on these complex and largely undocumented issues.
A less-harmful version of masquerading is presenting an idealized version of yourself in online communication. Is there an ethical issue in representing yourself as younger, older, more attractive, more wealthy, or somehow more desirable? There is clearly a line, but where is it? If you are a convicted murderer, you will probably conceal that in online communication. What about minor crimes? Other traits that society cares about? People do this frequently in everyday life. One would not disclose parking offences at a job interview, unless perhaps the job involved driving.
Stalking and snooping
Stalking is the obsession with the whereabouts and activities of another. The internet enables new forms of stalking, which might or might not be dangerous to the object of this interest. It is probably not a violation of any law of any country for an ex-husband to masquerade as a lonely middle-aged woman and try to befriend his ex-wife online, but many people consider such behaviour unethical.
There is an increasing number of public sources of data about individuals that might better be kept private. It is against the law to amass such data in some countries, but not in others. Should there be international discussion of the ethics of such databases? Is it ethical for a citizen of a country in which the law protects privacy to use a paid service in another country to find out information about his neighbours?
Online gambling is illegal in some countries. But there are online casinos in countries where it is legal, and they all take credit cards. Is it ethical to take advantage of the global nature of the internet to circumvent national laws? It is certainly easy. Another example, perhaps closer to home, is copyright law. Within the United Kingdom, the current text of the Book of Common Prayer and the Authorized Version of the Bible are the property of the Crown in perpetuity, and rights to it are exercised by the Crown Printer. But nothing prevents someone in, say, the United States from putting that material on a freely-available web server.
Because of the ease of posing, the ease of forming communities, and the difficulty in determining authenticity, it's easy to use the internet to monger hate and to spread lies. There is no point giving free publicity to any hatemonger's web site by mentioning it specifically, but the ease of making such a site and its global reach is problematic. If a country has laws about such sites, but the physical facilities providing the information are in another country, it is not at all obvious what to do. Some totalitarian countries have built a firewall around their country's access to global information, allowing nothing in or out without the permission of the government. That approach, while it might solve the hatemongering problem, certainly creates others.
For many years, some governments have held that it is important that they be able to intercept and read any correspondence by or to their citizens. One large European country bans encryption technology entirely. The United States treats encryption technology as a weapon, and controls the export of high-quality encryption software in the same way that it controls the export of most military weapons.
Because the mechanisms of the internet are decentralized, and because encryption can be done entirely in software, it is difficult to regulate the ability of the public to use military-grade encryption technology. The mathematics of encryption are widely known. The ethical issues in the use of encryption in everyday life are not well understood.
It is easy to find academic papers on the internet. Students from preteens to doctoral candidates place their written work online, for a wide variety of reasons. Does this form an attractive nuisance? Almost every educational institution has rules against plagiarism, but these days it is almost impossible for a teacher to track down the source of plagiarized material. Is it unethical to place such material online? To index it?
Search and index
There are hundreds of search engines, topic indexes, and directory services whose purpose is to help people find online whatever they are looking for. Should the operator of a search engine be held responsible for that engine's discovery of unethical material? Is the operator of an index computer that indexes 300 million pages responsible for searching them to remove child pornography, hatemongering, mail order weapons companies, or vendors of illegal drugs? If they are, then who pays for it? If they are not, then who is responsible if a child in Peru uses a search engine in Aruba to locate a gun for sale in Texas, buys it, and commits a crime?